Conductivity Diffusivity Research Articles

Quantized Seebeck coefficient of quasi-ballistic gold nanowires

The behavior of the Seebeck coefficient in the intermediate regime between atomic scale ballistic conduction and bulk-like diffusive conduction remains unclear. To address this, we have developed a microscale device capable of simultaneously measuring the Seebeck coefficient and electrical conductance of gold nanowires in an adiabatic environment. The nanowires were made in situ by electromigration from lithographically prepared bow-tie electrodes, yielding a wide range of wire thicknesses down to a few hundred atoms. We observed quantization of the Seebeck coefficient, a phenomenon previously observed only at the Ångstrom scale, in relatively thick wires with a thickness of several tens of nanometers. The quantized Seebeck coefficient was proportional to the reciprocal of the electrical conductance with a slope of −47.8 μV/K, indicating that electrons are spatially confined due to the electronic shell structure of the nanowire, similar to the quantization of electrical conductance.

Thermal processes affected by carbon dioxide near ground surface

This study provides penetrative investigation of the effects of carbon dioxide concentration on time-dependent temperature and energy fluxes on the ground surface subject to solar irradiation. While global warming significantly impacts human life, the factors responsible remain controversial. This work considers unsteady one-dimensional heat conduction and radiative heat transfer, including collimated and diffuse components as functions of longitude, latitude, and altitude. Diffuse radiation depends on the different absorption bands of carbon dioxide and water vapor, as functions of wavelength, temperature, concentrations or pressure. The predicted results using COMSOL computer code show that the effects of carbon dioxide concentration on ground surface temperature are negligibly small, for example, over a 5-year period. Time-dependent ground surface temperature strongly depends on the absorption or dissipation of diffuse radiation and heat conduction. Diffuse radiation has a damping effect on temperature variation. Temperature changes due to solar irradiation absorption in the atmosphere are also negligibly small, despite solar irradiation being much greater than diffuse radiation and heat conduction. The absorption or dissipation of diffuse radiation depends on the dominant absorption bands centered at 4.3 and 15 μm of carbon dioxide at different times. This study, from the viewpoint of energy conservation, identifies diffuse radiation as a critical factor influencing the rate of temperature change at the ground surface, without assuming radiative or thermal equilibrium or modeling convection. Poor management of this radiation would hinder efforts to avoid droughts, water scarcity, severe fires, rising sea levels, flooding, catastrophic storms, and biodiversity loss.

Chloroplast ATP synthase restricts photosynthesis under fluctuating light in tomato but not in maize

Photosynthesis in fluctuating light requires coordinated adjustments of diffusion conductance and biochemical capacity, but the role of chloroplast ATP synthase activity (gH+) in dynamic photosynthesis is not well understood. In this study, we measured gas exchange, chlorophyll fluorescence and electrochromic shift signals in fluctuating light for leaves of tomato (Solanum lycopersicum) and maize (Zea mays). During the transition from sun to shade, simultaneous increases in gH+, effective quantum yield of PSII, and net CO2 assimilation rate (AN) occurred in tomato but uncoupled in maize, indicating that gH+ limited AN during the sun-to-shade transition in tomato but not in maize. During the shade-to-sun transition, gH+ increased simultaneously with stomatal conductance, mesophyll conductance and Rubisco carboxylation capacity in tomato, suggesting that gH+ is an overlooked factor affecting light induction of AN in tomato. By comparison, gH+ maintained at high levels in maize and its AN was mainly restricted by stomatal conductance. Our results reveal that the kinetics of gH+ in fluctuating light differs between species, and chloroplast ATP synthase may be a potential target for improving dynamic photosynthesis in crops such as tomato.

Thermal Conductivity of AlSi10MnMg Alloy in Relation to Casting Technology and Heat Treatment Method.

Nowadays, with the development of electromobility, the requirements not only for the mechanical properties but also for the thermal conductivity of castings are increasing. This paper investigates the influence of casting and heat treatment technology on the thermal diffusivity and thermal conductivity of an AlSi10MnMg alloy. The thermal diffusivity was monitored as a function of temperature in the range of 50-300 °C for the material cast by high-pressure die casting (HPDC) and also by gravity sand casting (GSC) and gravity die casting (GDC). This study also investigated the effect of the T5 heat treatment temperature (artificial ageing without prior solution treatment-HT200, HT300, and HT400) on the thermal conductivity of the material cast by different technologies. Experiments confirmed that the thermal diffusivity or thermal conductivity of the alloy depends on the casting technology. The slower the cooling rate of the casting, the higher the thermal conductivity value. For the alloy in the as-cast condition, the thermal conductivity at 50 °C is in the range of about 125 to 138 [W·m-1·K-1]. Regardless of the casting method, the thermal conductivity tends to increase with temperature (50-300 °C). Furthermore, a positive effect of heat treatment without prior solution treatment (HT200, HT300, and HT400) on the thermal conductivity was demonstrated. Regardless of the casting method of the samples, the thermal conductivity also increases with increasing heat treatment temperature. The results further showed that when artificial ageing is performed in industrial practice on castings to increase mechanical properties in the temperature range of 160-230 °C, this heat treatment has a positive effect on thermal conductivity.

CoAl-LDH on ZIF-67 template inserted into the conductive matrix as a high-efficiency composite anode for facilitating phosphorus elimination

Phosphorus pollution can induce water eutrophication and critically threaten the stability of the aquatic ecosystem. Capacitive deionization (CDI) is a potential candidate for controlling phosphorus levels due to its lack of chemical requirements, eco-friendliness, and low energy demand. Herein, a novel ZIF-67-derived CoAl-LDH embedded in conductive carbon skeletons (CoAl-LDH/C) was successfully constructed by a self-sacrificial template strategy. A conductive carbon matrix is incorporated into LDH, which can alleviate the insufficient conductivity and aggregation issues for LDH. The results revealed that CoAl-LDH/C possesses superior phosphorus elimination properties (qm=32.7 mg P/g) at 1.2 V, benefiting from its abundant active sites, large mesoporous diameter, specific surface area, total pore volume, outstanding specific capacitance, and ion diffusion. Meanwhile, the energy consumption of CoAl-LDH/C is merely 3.398 kWh/kg and 0.024 kWh/m3. CoAl-LDH/C also proved flexible for practical applications regarding complex water quality (wide pH range, coexisting substances, natural water) and cyclic utilization. Finally, the potential mechanism illuminated that the phosphorus elimination process in an electric field engages with ligand exchange, anion exchange, electrostatic attraction, and hydrogen bonds. This work paves a promising concept for designing innovative LDH-based electrodes with excellent ion diffusion and superior conductivity to eliminate phosphorus efficiently.

The strength and hydraulic conductivity characteristics of sewage sludge ash and natural soil mixtures – a sustainable alternate landfill liner material

ABSTRACT This paper examines the feasibility of the natural soil and sewage sludge ash (SSA) mixtures, which satisfy the criteria to be used as landfill liners. The effect of SSA content on hydraulic conductivity and strength characteristics of natural soil and SSA mixtures has been investigated through a series of laboratory tests. The results demonstrate that mixtures exhibit an increase in both hydrodynamic diffusion coefficient and strength with the increasing SSA content. With the content of SSA from 0% to 5%, the values of the hydrodynamic diffusion coefficient ( D ) ranged from 3.5 × 10−10 to 15 × 10−10 cm2/s. The increase in the hydrodynamic diffusion coefficient is minor for low SSA content and significant for SSA content exceeding 5%. The inclusion of 5% SSA content results in a hydrodynamic diffusion coefficient that is approximately three times higher than that observed in natural soil. The results were obtained from soil triaxial tests, revealing that the mixtures containing SSA exhibited a significant increase in both the initial tangent modulus and the ultimate principal stress difference compared to those of natural soil. The SSA content with the highest value exhibits maximum initial tangent modulus and ultimate principal stress. The comprehensive analysis of the strength and hydraulic diffusion conductivity of the mixtures demonstrates that the incorporation of 3% SSA results in a significant enhancement in strength, while marginally increasing hydrodynamic diffusion coefficients. Therefore, it can be inferred that the utilization of mixtures containing 3% SSA content as a liner material is suitable.

Investigation of heat generation and radiation effects on boundary layer flow of Prandtl liquid with Cattaneo–Christov double diffusion models

In this analysis, a bidirectional stretched sheet is used to produce a 3D\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{D}$$\\end{document} flow of Prandtl liquid with improve mass diffusion and heat conduction models. This study advances knowledge of magnetohydrodynamics, radiation impacts, and heat production in fluid dynamics and transport processes. The Prandtl fluid model is critical for modeling non-Newtonian fluids, capturing its viscoelastic features, and allowing for precise simulation in industrial applications. It gives a mathematical foundation for analyzing complex fluid behaviors, which is necessary for optimizing operations utilizing such fluids. It uses the boundary layer method to simplify the fundamental equations and Cattaneo–Christov double diffusion models. The optimal homotopy analysis method is used to solve nonlinear ODEs caused by non-dimensional similarity variables. This investigation undertakes the calculation of drag coefficient for surfaces mass transfer rates and heat transfer rates proximate to the solid boundary. Furthermore, it conducts a comprehensive analysis of the influences exerted by various parameters on concentration and temperature profiles employing graphical representations for a rigorous examination. The Prandtl fluid model describes the viscoelastic characteristics of non-Newtonian fluids through constitutive equations, dimensional evaluation, and numerical simulations, which are frequently validated by experiments. The results show that changes in thermal and concentration relaxation parameters are accompanied by a decline in temperature. Temperature field rises as the thermal radiation parameter and heat generation increases. The work's novelty consists in its advanced modeling of Prandtl non-Newtonian fluids via Cattaneo–Christov double diffusion models, which incorporate magnetohydrodynamics and radiation effects and use optimal homotopy analysis for accurate parametric analyses of heat and mass transfer.

Utilizing numerical techniques for modeling radiating Casson nanofluid flow with thermophoretic phenomenon on a heated stretching surface

This work aims to use mathematical modeling to investigate the mechanics of heat and mass transport in dissipative Casson nanofluid flows over a linear rough sheet. This study considers various elements such as thermal radiation, magnetic fields, heat generation, the varied properties of porous media, and the thermophoretic impact. Besides that, it looks into the variations in viscosity, diffusivity, and thermal conductivity, as well as the energy dissipation from viscous internal friction and fluid temperature modifications. The method involves coming up with and changing the boundary layer equations into a group of linked nonlinear ordinary differential equations that use variables that do not have any dimensions. The foundation of the solution strategy for these equations is the Hermite collocation method (HCM), which is renowned for its precision and adaptability. It offers an organized approach to solving the complex differential equations, allowing for accurate numerical solutions. The use of graphical representations ensures thorough data analysis and clarity, while also providing insightful information about the computed outcomes. The code validation method uses numerical comparisons with recent research to confirm the algorithm’s accuracy and dependability, as well as its resilience in comparison to the existing literature. Important conclusions from the study show that thermal boundary layers and nanofluid velocity decrease with increases in the porosity parameter, slip parameter, and magnetic field parameter.

An impedance spectroscopy study to unravel the effect of water on proton and oxygen transport in PEM fuel cells

A recent physics-based model for liquid and gaseous water transport in the cathode catalyst layer (CCL) is incorporated into our 1d ＋ 1d model for the PEM fuel cell impedance. The model includes parametric dependencies of the CCL oxygen diffusivity and proton conductivity on the liquid saturation. Fitting of the 1d ＋ 1d model to experimental impedance spectra of a PEM fuel cell reveals two intriguing effects. Contrary to common belief, the liquid water saturation in the CCL is nearly independent of cell current density due to the growing liquid pressure gradient that drives liquid water removal from the CCL. Further, the “dry” oxygen diffusivity of the catalyst layer increases with cell current density. Apparently, at small current density, electrochemical conversion proceeds primarily in narrow pores, where the Knudsen oxygen diffusivity is low. With growing current density, larger and better connected pores with higher oxygen diffusivity dominate in the current conversion, leading to increase in effective oxygen diffusivity observed in impedance spectroscopy data.

Ionic conduction and cathodic properties of CaMO3 (M=Fe and Mn) electrode materials via molecular dynamics and first-principles simulations

Calcium-ion(Ca-ion) batteries are gaining ever-increasing attention for next-generation energy storage systems due to affordability, highly abundant, high energy density, high theoretical capacity, and low redox potential close to Li-ion. In this work, we deployed the first-principles and classical molecular dynamics simulations to investigate the electronic and diffusive properties of isostructural ternary perovskite CaMO3 (M= Fe and Mn). The transport properties at various temperatures from ion dynamics and electronic properties of CaMO3 perovskites are examined using classical molecular dynamics and quantum mechanical simulations, respectively. We present the microscopic origin of the diffusion of multivalent ions like Ca2+ within the crystal structure of perovskite material and the effects of two transition metals, manganese and iron. Dynamic studies of Ca-ions were performed using molecular dynamic simulation, which depicts the diffusivity and conductivity of Ca-ion in CaMO3 material. We find that the diffusivity in both the crystals increases with temperature; as a result, conductivity increases. Among both the crystals, CaFeO3 requires less activation energy for diffusion and ionic conduction than CaMnO3. Using density functional theory, we calculated specific capacity, electronic density of states, phase stability and equilibrium cell voltage, and charge transfer process during intercalation-deintercalation from first-principles calculations. The electronic behavior of these materials shows that CaFeO3 has better electronic and transport properties than CaMnO3.

A Multiple-physics coupled model for nanoconfined CO2-CH4 mixture transport behavior: Implications for CO2 geological storage in ultra-tight formation

Considerable efforts have been made to examine the feasibility of CO2-enhanced gas recovery (CO2-EGR), a promising approach for improving gas recovery by using CO2 to displace in-situ CH4 in ultra-tight gas reservoirs rich in nanopores. However, most research has focused on either single-component gas flow physics or competitive adsorption of multiple gas components in nanopores. The flow behavior of nanoconfined CO2-CH4 mixtures remains an area of knowledge gap. This work establishes a theoretical framework for CO2-CH4 mixture flow capacity by coupling mixture flow in the bulk region with surface diffusion in the adsorption area. Results indicate that: a) Total mixture flow conductance increases rapidly at pressures below ∼10 MPa, with CO2 contributing over 99 % to surface diffusion conductance; b) Increasing CO2 molar ratio from 0.2 to 0.8 can lead to a 167 % enhancement in total mixture conductance; c) Variations in CO2-CH4 competitive adsorption characteristics have little impact on total conductance.

Growth, optical and thermal properties of YbxSm1-xCa4O(BO3)3 crystals

YbxSm1-xCOB (x = 0.1, 0.2) crystals were grown by the Bridgman method for the first time. The purpose of this paper is to evaluate the application prospect of Yb:SmCOB crystal in quasi-parametric chirped pulse amplification (QPCPA) and frequency-doubling laser. The phase structure, thermal properties and optical properties of Yb:SmCOB were studied, and the density of states of SmCOB crystal was calculated by first-principles. The effective segregation coefficient Keff of Yb0.1Sm0.9COB and Yb0.2Sm0.8COB crystals are 0.89 and 0.88, respectively. The thermal diffusivity and thermal conductivity of Yb:SmCOB decrease with increasing temperature. The specific heat increases with the increase of temperature and eventually tends to be constant. The specific heat of Yb:SmCOB crystal is greater than 0.70 J/(g·K) at room temperature. The transmittance of Yb:SmCOB crystal reaches 87 % in the range of 500 ∼ 900 nm. With the increase of Yb3+ doping concentration, the UV absorption cut-off edge is red shifted. The frequency doubling emission peak of Yb:SmCOB crystal at 490 nm was measured by 980 nm laser. Yb:SmCOB has the characteristics of high transmittance and high specific heat, and has application potential in laser frequency doubling and QPCPA.

The g-C3N4/rGO composite for high-performance supercapacitor: Synthesis, characterizations, and time series modeling and predictions

Supercapacitors have gathered significant interest in addressing the increasing need for energy storage devices with high power and energy densities. This study introduces a composite framework designed to enhance supercapacitor performance by leveraging the synergistic effects of g-C3N4/rGO composite. The composite electrode, which combines rGO for high conductivity and g-C3N4 for rapid ion diffusion, demonstrates excellent supercapacitor performance. The synthesized materials were characterized using different analytical tools such as X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller, Scanning and Transmission electron microscope, and X-ray photoelectron spectroscopy. The composite electrode exhibited outstanding performance characteristics, including a specific capacitance of 407.7 F/g, an energy density of 11.4 W h/kg, and a high power density of 186.7 W/kg. Kinetic analysis revealed that the g-C3N4/rGO composite electrode has a dominant diffusive controlled process. The g-C3N4/rGO electrode also demonstrated exceptional durability, maintaining remarkable capacitance retention even after the 5000th charge/discharge cycles. Moreover, the cyclic stability and Coulombic efficiency of the g-C3N4/rGO electrode were modeled and predicted by utilizing the time series analysis technique (Holt-Winters exponential smoothing). Considering the overall results, the g-C3N4/rGO composite electrode has a great potential for energy storage applications.

Muscle microvascular oxygen delivery limitations during the contraction phase of intermittent maximal effort contractions.

The end-test torque (ETT) during intermittent maximal effort contractions reflects the highest contraction intensity at which a muscle metabolic steady-state can be attained. This study determined if ETT is the highest intensity at which the contraction phase of intermittent exercise does not limit the matching of microvascular oxygen delivery to muscle oxygen demand. Microvascular oxygenation characteristics of the biceps brachii muscle were measured in sixteen young, healthy individuals (8M/8F, 22 ± 3years, 80.9 ± 20.3kg) by near-infrared spectroscopy during maximal effort elbow flexion under control conditions (CON) and with complete circulatory occlusion (OCC). Increases in total-[heme] were blunted during OCC compared to CON (225 ± 87 vs. 264 ± 88μM, p < 0.001) but OCC did not elicit a compensatory increase in deoxygenated-[heme] at any timepoint (108 ± 62 vs. 101 ± 61μM, p > 0.05). Deoxygenated-[heme] was significantly elevated during contraction, relative to relaxation, above ETT (107 ± 60 vs. 98.8 ± 60.5μM, p < 0.001), but not at ETT (91.7 ± 54.1 vs. 98.4 ± 62.2μM, p = 0.174). Total-[heme] was significantly reduced during contraction, relative to relaxation, at all contraction intensities during CON (p < 0.05) and OCC (p < 0.05). These data suggest that ETT may reflect the highest contraction intensity at which contraction-induced increases in intramuscular pressures do not limit muscle perfusion to a degree that requires further increases in fractional oxygen extraction (i.e., deoxygenated-[heme]) despite limited microvascular diffusive conductance (i.e., total-[heme]).

Large scale atomistic and quantum mechanical study of Na+ ion transport in liquid electrolytes for batteries

Lithium–ion batteries (LIBs) have long dominated energy storage markets due to their high energy density and reliability. However, concerns over lithium scarcity and geographic distribution necessitate alternatives. Sodium-ion batteries (SIBs) offer a promising solution due to sodium's abundance, cost-effectiveness, and favorable electrochemical properties. This study investigates Na+ ion transport, aggregation, and performance in various organic electrolytes using molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The electrolytes studied include ethylene carbonate (EC), propylene carbonate (PC), dimethoxyethane (DME), and dimethyl carbonate (DMC) at 320 K. We focused on conductivity, diffusivity, and survival probability of Na+ ions at different salt concentrations. Furthermore, the solvation structure and the binding energy of ions in the electrolytes are thoroughly analyzed. Key findings reveal that at 2 M salt concentration, Na+ ion diffusivity and ionic conductivity follow the order EC>PC>DME>DMC. Increasing salt concentration decreases self–diffusion coefficients of Na+ and PF6− ions across all electrolytes, affecting conductivity. EC shows the highest ionic conductivity at both 1 M and 2 M salt concentrations. These insights suggest that a 2 M NaPF6 concentration in EC optimizes ionic conductivity, making it ideal for high–performance SIBs. This study provides crucial understanding for optimizing electrolytes in SIBs, advancing their development for scalable energy storage solutions.

Operation parameters study on the performance of PEMFC based orthogonal test method

By selecting five key operational parameters—inlet temperature, operating temperature, anode humidity, cathode humidity, and operating pressure—and using PEMFC power density, membrane temperature difference, and membrane water content as performance indicators, simulations were conducted using 3D CFD modeling and orthogonal experiments to identify the most significant factors influencing PEMFC performance and determine the optimal operational parameter combination. The results show that working pressure has the most significant impact on PEMFC performance. Pressure variations cause significant changes in diffusion and heat conduction within the PEMFC. When the working pressure increases from 1.0 MPa to 3.0 MPa, the power density increases by approximately 11.2 %, but the temperature difference within the membrane increases by about 30.5 %. The difference between operating temperature and inlet temperature directly leads to changes in the temperature difference within the membrane. Moreover, changes in operating temperature greatly affect the water content within the proton exchange membrane, which in turn impacts the PEMFC's power density. When the operating temperature increases from 60 °C to 100 °C, the water content within the membrane decreases by approximately 50.5 %, and the power density decreases by 60.4 %. By optimizing the combination of operating parameters using a comprehensive scoring method, the temperature difference within the membrane can be controlled at 27.78 °C while ensuring the power density is increased to 0.92 W/cm2.

A comparative numerical investigation of effect of mechanical compression on the transport properties of gas diffusion layer fabricated by wet and dry laid methods

The gas diffusion layer (GDL), a core component of the proton exchange membrane fuel cell (PEMFC), is integral to thermoelectric and gas-liquid transport. Recognizing the impact of mechanical compression on transport properties and cell performance, it is crucial to comprehensively study the GDL's effect on effective transport performance. In this study, two types of GDLs, Toray GDL fabricated by wet-laid and Freudenberg GDL fabricated by dry-laid, are first reconstructed. Then, their stress-strain distributions under various mechanical compression ratios from 0 to 40 % are simulated using the finite element method, along with the effects of mechanical pressures on the microstructural parameters. Finally, a pore scale model is utilized to obtain the effective transport properties of the two types of GDLs under ten different compression ratios. The results show that Freudenberg GDL exhibits a more rapid stress transfer with a more uniformly distributed stress, while Toray GDL displays a slower stress transfer with a more differentially distributed stress. Notably, the pore size decreases significantly by approximately 60 % in both GDL types when the compression ratio increases from 0 % to 40 %. As the mechanical compression ratios increases from 0 to 40 %, the tortuosity of Toray GDL and Freudenberg GDL in the in-plane/through-plane direction increases by 78 %/50 % and 81 %/86 %, respectively. The conductivity of Toray GDL and Freudenberg GDL increases by 150 %/650 % and 130 %/140 % in the in-plane/through-plane direction, respectively, when the compression ratio is increased to 40 %. Additionally, a 20 % compression ratio is identified as an optimal point for both GDLs to balance gas diffusion and thermoelectric conduction.

Exact relations between the conductivities and their connection to the chemical composition of QCD matter

We present exact relations between the diffusion coefficients or conductivities, κqq′/T=σqq′, of strongly interacting matter. We show that once the diagonal entries are known in two different charge representations, the off-diagonal coefficients are functions of the diagonal entries once isospin symmetry applies. As an important example, we infer the conductivities on the basis of available calculations from lattice quantum chromodynamics and argue that these computations suffer under the approximations made to achieve them. Further, we argue that the representation of the conductivities with respect to the conserved quark flavors may deliver more insight into the chemical composition of strongly interacting matter. Published by the American Physical Society 2024

Controllable preparation of carbon coating Ge nanospheres with a cubic hollow structure for high-performance lithium ion batteries

Germanium based nanomaterials are very promising as the anodes for the lithium ion batteries since their large specific capacity, excellent lithium diffusivity and high conductivity. However, their controllable preparation is still very difficult to achieve. Herein, we facilely prepare a unique carbon coating Ge nanospheres with a cubic hollow structure (Ge@C) via a hydrothermal synthesis and subsequent pyrolysis using low-cost GeO2 as precursors. The hollow Ge@C nanostructure not only provides abundant interior space to alleviate the huge volumetric expansion of Ge upon lithiation, but also facilitates the transmission of lithium ions and electrons. Moreover, experiment analyses and density functional theory (DFT) calculations unveil the excellent lithium adsorption ability, high exchange current density, low activation energy for lithium diffusion of the hollow Ge@C electrode, thus exhibiting significant lithium storage advantages with a large charge capacity (1483 mAh/g under 200 mA g−1), distinguished rate ability (710 mAh/g under 8000 mA g−1) as well as long-term cycling stability (1130 mAh/g after 900 cycles under 1000 mA g−1). Therefore, this work offers new paths for controllable synthesis and fabrication of high-performance Ge based lithium storage nanomaterials.

Identifying the Mechanisms of a Peripherally Limited Exercise Phenotype in Patients With Heart Failure With Preserved Ejection Fraction.

We identified peripherally limited patients using cardiopulmonary exercise testing and measured skeletal muscle oxygen transport and utilization during invasive single leg exercise testing to identify the mechanisms of the peripheral limitation. Forty-five patients with heart failure with preserved ejection fraction (70±7 years, 27 females) completed seated upright cardiopulmonary exercise testing and were defined as having a (1) peripheral limitation to exercise if cardiac output/oxygen consumption (VO2) was elevated (≥6) or 5 to 6 with a stroke volume reserve >50% (n=31) or (2) a central limitation to exercise if cardiac output/VO2 slope was ≤5 or 5 to 6 with stroke volume reserve <50% (n=14). Single leg knee extension exercise was used to quantify peak leg blood flow (Doppler ultrasound), arterial-to-venous oxygen content difference (femoral venous catheter), leg VO2, and muscle oxygen diffusive conductance. In a subset of participants (n=36), phosphocreatine recovery time was measured by magnetic resonance spectroscopy to determine skeletal muscle oxidative capacity. Peak VO2 during cardiopulmonary exercise testing was not different between groups (central: 13.9±5.7 versus peripheral: 12.0±3.1 mL/min per kg; P=0.135); however, the peripheral group had a lower peak arterial-to-venous oxygen content difference (central: 13.5±2.0 versus peripheral: 11.1±1.6 mLO2/dL blood; P<0.001). During single leg knee extension, there was no difference in peak leg VO2 (P=0.306), but the peripherally limited group had greater blood flow/VO2 ratio (P=0.024), lower arterial-to-venous oxygen content difference (central: 12.3±2.5 versus peripheral: 10.3±2.2 mLO2/dL blood; P=0.013), and lower muscle oxygen diffusive conductance (P=0.021). A difference in magnetic resonance spectroscopy-derived phosphocreatine recovery time was not detected (P=0.199). Peripherally limited patients with heart failure with preserved ejection fraction identified by cardiopulmonary exercise testing have impairments in oxygen transport and utilization at the level of the skeletal muscle quantified by invasive knee extension exercise testing, which includes an increased blood flow/V̇O2 ratio and poor muscle diffusive capacity. URL: https://www.clinicaltrials.gov; Unique identifier: NCT04068844.