Compact step-added T-type PAC for enhanced hydrogen detection: A photoacoustic frequency shift approach.

In this study, we introduce an innovative photoacoustic frequency shift (PAFS) technique for hydrogen (H2) detection, complemented by both theoretical models and practical experiments. To mitigate cross-sensitivity, we analyzed the sound speeds of six different gases, confirming minimal interference with H2 due to significant velocity disparities. Central to our approach is the design of a miniaturized step-added T-type Photoacoustic Cell (PAC), with parameters meticulously optimized for enhanced performance. Using COMSOL Multiphysics' Thermal Viscous Acoustics module, we conducted simulations to evaluate the quality factor and acoustic pressure, both crucial for the sensor's efficiency. Additionally, we assessed the system's stability, influenced by gas flow, through gas velocity distribution analyses using the Computational Fluid Dynamics module. Experimental investigations focused on the system's sensing performance, revealing a distinct frequency shift of âˆ¼45 Hz for every 1 % change in H2 concentration, with a high linear correlation (R2 = 0.99825). The system's response and recovery times were measured at 1.09 s and 1.25 s, respectively. Long-term stability, evaluated over 3000 s using Allan deviation, indicated a minimum detection limit (MDL) of 102.47 ppm at an integration time of 375 s. These findings validate the efficacy of the step-added T-type PAC in H2 detection.

Operando Spectroscopy to Understand Dynamic Structural Changes of Solid Catalysts.

Solid materials like heterogeneous catalysts are highly dynamic and continuously tend to change when exposed to the reaction environment. To understand the catalyst system under true reaction conditions,operando spectroscopy is the key to unravel small changes, which can ultimately lead to a significant difference in catalytic activity and selectivity. This was also the topic of the 7th International Congress on Operando Spectroscopy in Switzerland in 2023. In this article, we discuss various examples to introduce and demonstrate the importance of this area, including examples from emission control for clean air (e.g. CO oxidation), oxidation catalysis in the chemical industry (e.g. oxidation of isobutene), future power-to-X processes (electrocatalysis, CO2 hydrogenation to methanol), and non-oxidative conversion of methane. All of these processes are equally relevant to the chemical industry. Complementary operando techniques such as X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and Raman spectroscopy were utilized to derive the ultimate structure of the catalyst. The variety of conditions requires distinctly different operando cells that can reach a temperature range of 400-1000 °C and pressures up to 40 bar. The best compromise for both the spectroscopy and the catalytic reaction is needed. As an outlook, we highlight emerging methods such as modulation-excitation spectroscopy (MES) or quick-extended X-ray absorption fine structure (QEXAFS) and X-ray photon in/out techniques, which can provide better sensitivity or extend X-ray based operando studies.

Pure-Water-Fed Forward-Bias Bipolar Membrane CO2 Electrolyzer.

Coupling renewable electricity to reduce carbon dioxide (CO2) electrochemically into carbon feedstocks offers a promising pathway to produce chemical fuels sustainably. While there has been success in developing materials and theory for CO2 reduction, the widespread deployment of CO2 electrolyzers has been hindered by challenges in the reactor design and operational stability due to CO2 crossover and (bi)carbonate salt precipitation. Herein, we design asymmetrical bipolar membranes assembled into a zero-gap CO2 electrolyzer fed with pure water, solving both challenges. By investigating and optimizing the anion-exchange-layer thickness, cathode differential pressure, and cell temperature, the forward-bias bipolar membrane CO2 electrolyzer achieves a CO faradic efficiency over 80% with a partial current density over 200 mA cm-2 at less than 3.0 V with negligible CO2 crossover. In addition, this electrolyzer achieves 0.61 and 2.1 mV h-1 decay rates at 150 and 300 mA cm-2 for 200 and 100 h, respectively. Postmortem analysis indicates that the deterioration of catalyst/polymer-electrolyte interfaces resulted from catalyst structural change, and ionomer degradation at reductive potential shows the decay mechanism. All these results point to the future research direction and show a promising pathway to deploy CO2 electrolyzers at scale for industrial applications.

Development of in situ high resolution NMR: Proof-of-principle for a new (spinning) cylindrical mini-pellet approach applied to a Lithium ion battery.

Solid-state nuclear magnetic resonance (ssNMR) spectroscopy is a powerful technique for characterizing the local structure and dynamics of battery and other materials. It has been widely used to investigate bulk electrode compounds, electrolytes, and interfaces. Beside common ex situ investigations, in situ and operando techniques have gained considerable importance for understanding the reaction mechanisms and cell degradation of electrochemical cells. Herein, we present the recent development of in situ magic angle spinning (MAS) NMR methodologies to study batteries with high spectral resolution, setting into context possible advances on this topic. A mini cylindrical cell type insert for 4 mm MAS rotors is introduced here, being demonstrated on a Li/VO2F electrochemical system, allowing the acquisition of high-resolution 7Li MAS NMR spectra, spinning the electrochemical cell up to 15 kHz.

Development of a versatile electrochemical cell for in situ grazing-incidence X-ray diffraction during non-aqueous electrochemical nitrogen reduction.

In situ techniques are essential to understanding the behavior of electrocatalysts under operating conditions. When employed, in situ synchrotron grazing-incidence X-ray diffraction (GI-XRD) can provide time-resolved structural information of materials formed at the electrode surface. In situ cells, however, often require epoxy resins to secure electrodes, do not enable electrolyte flow, or exhibit limited chemical compatibility, hindering the study of non-aqueous electrochemical systems. Here, a versatile electrochemical cell for air-free in situ synchrotron GI-XRD during non-aqueous Li-mediated electrochemical N2 reduction (Li-N2R) has been designed. This cell not only fulfills the stringent material requirements necessary to study this system but is also readily extendable to other electrochemical systems. Under conditions relevant to non-aqueous Li-N2R, the formation of Li metal, LiOH and Li2O as well as a peak consistent with the α-phase of Li3N was observed, thus demonstrating the functionality of this cell toward developing a mechanistic understanding of complicated electrochemical systems.

Microbial electrosynthesis of acetate from CO2 in three-chamber cells with gas diffusion biocathode under moderate saline conditions.

The industrial adoption of microbial electrosynthesis (MES) is hindered by high overpotentials deriving from low electrolyte conductivity and inefficient cell designs. In this study, a mixed microbial consortium originating from an anaerobic digester operated under saline conditions (∼13 g L-1 NaCl) was adapted for acetate production from bicarbonate in galvanostatic (0.25 mA cm-2) H-type cells at 5, 10, 15, or 20 g L-1 NaCl concentration. The acetogenic communities were successfully enriched only at 5 and 10 g L-1 NaCl, revealing an inhibitory threshold of about 6 g L-1 Na+. The enriched planktonic communities were then used as inoculum for 3D printed, three-chamber cells equipped with a gas diffusion biocathode. The cells were fed with CO2 gas and operated galvanostatically (0.25 or 1.00 mA cm-2). The highest production rate of 55.4 g m-2 d-1 (0.89 g L-1 d-1), with 82.4% Coulombic efficiency, was obtained at 5 g L-1 NaCl concentration and 1 mA cm-2 applied current, achieving an average acetate production of 44.7 kg MWh-1. Scanning electron microscopy and 16S rRNA sequencing analysis confirmed the formation of a cathodic biofilm dominated by Acetobacterium sp. Finally, three 3D printed cells were hydraulically connected in series to simulate an MES stack, achieving three-fold production rates than with the single cell at 0.25 mA cm-2. This confirms that three-chamber MES cells are an efficient and scalable technology for CO2 bio-electro recycling to acetate and that moderate saline conditions (5 g L-1 NaCl) can help reduce their power demand while preserving the activity of acetogens.

Engineering Array-Patterned Cathodes and Anodes for Synergistically Enabling High-Performance Lithium Metal Batteries.

Critical challenges such as safety and cyclability concerns resulting from the uncontrollable dendritic lithium (Li) growth, especially during the fast charging/discharging process, have seriously hampered the commercialization of Li metal batteries (LMBs). Here, a novel array-patterned LiFePO4 (LFP) cathode prepared via a simple, scalable calendaring method is developed to enable highly stable Li metal anodes with patterned ditches and bulges during the cell assembling process. Both the structured electrodes provide a remarkably increased electroactive surface area to lower the current density locally, facilitating Li-ion transport kinetics and homogeneous Li plating/stripping. Due to the long-term internal pressure in the cell, the structured LFP and Li electrodes can maintain their original structure during sustained cycling. Such distinctive electrode architectures and cell design synergistically enable excellent rate capability with a discharge capacity of up to 128 mA h g-1 at a high current density of 9 mA cm-2 and impressive cycling stability, with 89.6% capacity retention after 300 cycles at 1.5 mA cm-2. Moreover, ultrasonic transmission mapping is carried out and demonstrates no gas behavior in operating modified Li||LFP pouch cells over prolonged cycling. This simple fabrication method can potentially be applied to many other active materials to enable practical LMBs with high performance.

Desalination Using the Capacitive Deionization Technology with Graphite/AC Electrodes: Effect of the Flow Rate and Electrode Thickness.

Capacitive deionization (CDI) is an emerging water desalination technology whose principle lies in ion electrosorption at the surface of a pair of electrically charged electrodes. The aim of this study was to obtain the best performance of a CDI cell made of activated carbon as the active material for water desalination. In this work, electrodes of different active layer thicknesses were fabricated from a slurry of activated carbon deposited on graphite sheets. The as-prepared electrodes were characterized by cyclic voltammetry, and their physical properties were also studied using SEM and DRX. A CDI cell was fabricated with nine pairs of electrodes with the highest specific capacitance. The effect of the flow rate on the electrochemical performance of the CDI cell operating in charge-discharge electrochemical cycling was analyzed. We obtained a specific absorption capacity (SAC) of 10.2 mg/g and a specific energetic consumption (SEC) of 217.8 Wh/m3 at a flow rate of 55 mL/min. These results were contrasted with those available in the literature; in addition, other parameters such as Neff and SAR, which are necessary for the characterization and optimal operating conditions of the CDI cell, were analyzed. The findings from this study lay the groundwork for future research and increase the existing knowledge on CDI based on activated carbon electrodes.

Transcervical Versus Transfemoral Approach in Carotid Stenting Real World Experience in a Community Hospital.

INTRODUCTION: Peri-procedural embolic events are the Achilles' heel of carotid stenting. To overcome this complication, transcervical access to the carotid artery was introduced. In this study we describe our "our life" experience with the transcervical approach in a community hospital. MATERIAL AND METHODS: All carotid stent procedures between January 2010 and December 2020 were included in this retrospective analysis. The transcervical approach was compared to the transfemoral approach. In both procedures open-cell, closed-cell design and hybrid stents were used. In-hospital stroke was the primary outcome measure. RESULTS: A total of 340 procedures were performed, in 184 patients the transfemoral approach was used and in 156 patients the transcervical approach was used. In 12 patients (3.5%) an in-hospital stroke was diagnosed, 4 in the transfemoral group (2.2%) and 8 in the transcervical group (5.1%) (P = 0.14). In the multivariate analyses a symptomatic lesion was associated with in-hospital stroke. Neither type of access nor cell design was associated with increased risk of in-hospital stroke. CONCLUSIONS: In contrast to previous studies, we could not confirm the advantages of the transcervical approach. However, conclusions should be carefully drawn, since this study is retrospective and was performed with multiple surgeon and different kind of stents.

Computational design and analysis of modular cells for large libraries of exchangeable product synthesis modules.

Microbial metabolism can be harnessed to produce a large library of useful chemicals from renewable resources such as plant biomass. However, it is laborious and expensive to create microbial biocatalysts to produce each new product. To tackle this challenge, we have recently developed modular cell (ModCell) design principles that enable rapid generation of production strains by assembling a modular (chassis) cell with exchangeable production modules to achieve overproduction of target molecules. Previous computational ModCell design methods are limited to analyze small libraries of around 20 products. In this study, we developed a new computational method, named ModCell-HPC, that can design modular cells for large libraries with hundreds of products with a highly-parallel and multi-objective evolutionary algorithm and enable us to elucidate modular design properties. We demonstrated ModCell-HPC to design Escherichia coli modular cells towards a library of 161 endogenous production modules. From these simulations, we identified E. coli modular cells with few genetic manipulations that can produce dozens of molecules in a growth-coupled manner with different types of fermentable sugars. These designs revealed key genetic manipulations at the chassis and module levels to accomplish versatile modular cells, involving not only in the removal of major by-products but also modification of branch points in the central metabolism. We further found that the effect of various sugar degradation on redox metabolism results in lower compatibility between a modular cell and production modules for growth on pentoses than hexoses. To better characterize the degree of compatibility, we developed a method to calculate the minimal set cover, identifying that only three modular cells are all needed to couple with all compatible production modules. By determining the unknown compatibility contribution metric, we further elucidated the design features that allow an existing modular cell to be re-purposed towards production of new molecules. Overall, ModCell-HPC is a useful tool for understanding modularity of biological systems and guiding more efficient and generalizable design of modular cells that help reduce research and development cost in biocatalysis.

Progress in microbial fuel cell technology for wastewater treatment and energy harvesting.

The global energy crisis has stimulated the development of various forms of green energy technology such as microbial fuel cells (MFCs) that can be applied synergistically and simultaneously toward wastewater treatment and bioenergy generation. This is because electricigens in wastewater can act as catalysts for destroying organic pollutants to produce bioelectricity through bacterial metabolism. In this review, the factors affecting energy production are discussed to help optimize MFC processes with respect to design (e.g., single, double, stacked, up-flow, sediment, photosynthetic, and microbial electrolysis cells) and operational conditions/parameters (e.g., cell potential, microorganisms, substrate (in wastewater), pH, temperature, salinity, external resistance, and shear stress). The significance of electron transfer mechanisms and microbial metabolism is also described to pursue the maximum generation of power by MFCs. Technically, the generation of power by MFCs is still a significant challenge for real-world applications due to the difficulties in balancing between harvesting efficiency and upscaling of the system. This review summarizes various techniques used for MFC-based energy harvesting systems. This study aims to help narrow such gaps in their practical applications. Further, it is also expected to give insights into the upscaling of MFC technology while assisting environmental scientists to gain a better understanding on this energy harvesting approach.

The Role of Chimeric Antigen Receptor-T Cell Therapy in the Treatment of Hematological Malignancies: Advantages, Trials, and Tribulations, and the Road Ahead.

Immunotherapy is the upcoming trend in cancer treatment. Traditional cancer treatment methods include surgical resection, radiotherapy, chemotherapy, small molecule targeted drugs, monoclonal antibodies, and hematopoietic stem cell transplantation (HSCT). Surgical resection is useful for early-stage patients but not for metastatic cancer cells; radiotherapy and chemotherapy are more common but produce substantial damage to normal tissues and have poor selectivity. Targeted drugs, including monoclonal antibodies, have better comprehensive efficacy but can also encourage gene mutation of tumor cells and drug tolerance. HSCT is effective, but choosing a donor is often difficult, and the graft is also prone to rejection. Thus, chimeric antigen receptor (CAR)-T cell therapy, a form of cellular/adoptive immunotherapy, is at the forefront of cancer therapy treatments due to its sustained remission, fewer side effects, and a better quality of life. CAR-T cell therapy involves genetically modifying the T cells and multiplying their numbers to kill cancer cells. This review article gives an insight into how the CAR-T cells have evolved from simple T cells with modest immune function to genetically engineered robust counterparts that brought great hope in the treatment of hematological malignancies. Much research has been undertaken during the past decade to design and deliver CAR-T cells. This has led to successful outcomes in leukemias, lymphomas, and multiple myeloma, paving the way for expanding CAR therapy. Despite tremendous progress, CAR-T cell therapies are faced with many challenges. Areas for improvement include limited T cell persistence, tumor escape, immunosuppressive components in the tumor microenvironment, cancer relapse rate, manufacturing time, and production cost. In this manuscript, we summarize the innovations in the design and delivery of CAR technologies, their applications in hematological malignancies, limitations to its widespread application, latest developments, and the future scope of research to counter the challenges and improve its effectiveness and persistence.

Comparison of 2- and 3-compartment electrodialytic remediation cells for oil polluted soil from northwest Russia.

Electrodialytic remediation is a method based on electrokinetics, in which an electric field of low intensity increases the availability of pollutants in solid waste materials. The electric field induces processes that mobilise and transport inorganic and organic pollutants. The transport of ions in the electrodialytic cell is controlled by employing ion-exchange membranes, allowing separation of the electrodes from the solids. In this study, using a two cell design, electrodialytic experiments were conducted to compare remediation of a heavily oil-polluted soil from Arkhangelsk, Russia. The 2-compartment cell has not previously been employed for electrodialytic removal of organic pollutants and was tested along with the traditional 3-compartment design. The influence of experimental variables (current density, remediation time, stirring and light) and settings on the two cell designs was investigated. The highest removal (77%) of total hydrocarbons (THC) was observed in the 3-compartment cell at high current density (0.68 mA/cm2), longer remediation time (28 days), stirring and exposure to daylight. High current density and stirring increased the removal efficiencies in both cell designs. Within the studied experimental domain, the removal efficiencies in the 3-compartment cell (10-77%) were, however, higher than those observed in the 2-compartment cell (0-38%).

Moving Electrode Impedance Spectroscopy for Accurate Conductivity Measurements of Corrosive Ionic Media.

A measurement cell for the use of accurate conductivity measurements of corrosive ionic media is presented. Based on the concept of moving electrode electrochemical impedance spectroscopy, exceptional measurement accuracy is achieved in a large conductivity range. Extensive testing with corrosive ionic media demonstrated the robust operation of the cell under harsh chemical conditions, up to temperatures of 130 °C. The novel design allows monitoring small conductivity changes during chemical reactions in ionic media, for instance, zeolite formation from hydrated ionic liquids.

Development of a Genome-Scale Metabolic Model of Clostridium thermocellum and Its Applications for Integration of Multi-Omics Datasets and Computational Strain Design.

Solving environmental and social challenges such as climate change requires a shift from our current non-renewable manufacturing model to a sustainable bioeconomy. To lower carbon emissions in the production of fuels and chemicals, plant biomass feedstocks can replace petroleum using microorganisms as biocatalysts. The anaerobic thermophile Clostridium thermocellum is a promising bacterium for bioconversion due to its capability to efficiently degrade lignocellulosic biomass. However, the complex metabolism of C. thermocellum is not fully understood, hindering metabolic engineering to achieve high titers, rates, and yields of targeted molecules. In this study, we developed an updated genome-scale metabolic model of C. thermocellum that accounts for recent metabolic findings, has improved prediction accuracy, and is standard-conformant to ensure easy reproducibility. We illustrated two applications of the developed model. We first formulated a multi-omics integration protocol and used it to understand redox metabolism and potential bottlenecks in biofuel (e.g., ethanol) production in C. thermocellum. Second, we used the metabolic model to design modular cells for efficient production of alcohols and esters with broad applications as flavors, fragrances, solvents, and fuels. The proposed designs not only feature intuitive push-and-pull metabolic engineering strategies, but also present novel manipulations around important central metabolic branch-points. We anticipate the developed genome-scale metabolic model will provide a useful tool for system analysis of C. thermocellum metabolism to fundamentally understand its physiology and guide metabolic engineering strategies to rapidly generate modular production strains for effective biosynthesis of biofuels and biochemicals from lignocellulosic biomass.

Online Monitoring of Electrochemical Carbon Corrosion in Alkaline Electrolytes by Differential Electrochemical Mass Spectrometry.

Carbon corrosion at high anodic potentials is a major source of instability, especially in acidic electrolytes and impairs the long-term functionality of electrodes. In-depth investigation of carbon corrosion in alkaline environment by means of differential electrochemical mass spectrometry (DEMS) is prevented by the conversion of CO2 into CO3 2- . We report the adaptation of a DEMS system for online CO2 detection as the product of carbon corrosion in alkaline electrolytes. A new cell design allows for in situ acidification of the electrolyte to release initially dissolved CO3 2- as CO2 in front of the DEMS membrane and its subsequent detection by mass spectrometry. DEMS studies of a carbon-supported nickel boride (Nix B/C) catalyst and Vulcan XC 72 at high anodic potentials suggest protection of carbon in the presence of highly active oxygen evolution electrocatalysts. Most importantly, carbon corrosion is decreased in alkaline solution.

Design of an In-Operando Cell for X-Ray and Neutron Imaging of Oxygen-Depolarized Cathodes in Chlor-Alkali Electrolysis.

Oxygen-depolarized cathodes are a novel concept to be used in chlor-alkali electrolysis in order to generate significant energy savings. In these porous gas diffusion electrodes, hydrophilic and catalytically active microsized silver grains and a hydrophobic polytetrafluoroethylene cobweb structure are combined to obtain the optimum amount of three-phase boundaries between the highly alkaline electrolyte and the oxygen gas phase to achieve high current densities. However, the direct correlation between specific electrode structure and electrochemical performance is difficult. In this work, we report on the successful design and adaptation of an in-operando cell for X-ray (micro-computed tomography, synchrotron) and neutron imaging of an operating oxygen-depolarized cathode under realistic operation conditions, enabling the investigation of the electrolyte invasion into, and distribution inside, the porous electrode for the first time.

Evolution of Electrochemical Cell Designs for In-Situ and Operando 3D Characterization.

Lithium-based rechargeable batteries such as lithium-ion (Li-ion), lithium-sulfur (Li-S), and lithium-air (Li-air) cells typically consist of heterogenous porous electrodes. In recent years, there has been growing interest in the use of in-situ and operando micro-CT to capture their physical and chemical states in 3D. The development of in-situ electrochemical cells along with recent improvements in radiation sources have expanded the capabilities of micro-CT as a technique for longitudinal studies on operating mechanisms and degradation. In this paper, we present an overview of the capabilities of the current state of technology and demonstrate novel tomography cell designs we have developed to push the envelope of spatial and temporal resolution while maintaining good electrochemical performance. A bespoke PEEK in-situ cell was developed, which enabled imaging at a voxel resolution of ca. 230 nm and permitted the identification of sub-micron features within battery electrodes. To further improve the temporal resolution, future work will explore the use of iterative reconstruction algorithms, which require fewer angular projections for a comparable reconstruction.

Low-cost disposable high-pressure setup for in situ X-ray experiments.

A low-cost, flexible and fast method to create disposable sample cells suitable for in situ catalytic or material synthesis studies based on standard quartz capillaries, heat-shrinkable tubing and standard Swagelok components is described.

Effect of Open- vs Closed-Cell Stent Design on Periprocedural Outcomes and Restenosis After Carotid Artery Stenting: A Systematic Review and Comprehensive Meta-analysis.

PURPOSE: To compare periprocedural complications and in-stent restenosis rates associated with open- vs closed-cell stent designs used in carotid artery stenting (CAS). METHODS: A systematic search was conducted to identify all randomized and observational studies published in English up to October 31, 2017, that compared open- vs closed-cell stent designs in CAS. Identified studies were included if they reported the following outcomes: stroke, transient ischemic attack (TIA), myocardial infarction (MI), hemodynamic depression, new ischemic lesions detected on imaging, and death within 30 days, as well as the incidence of in-stent restenosis. A random-effects model meta-analysis was employed. Model results are reported as the odds ratio (OR) and 95% confidence interval (CI). The I2 statistic was used to assess heterogeneity. RESULTS: Thirty-three studies (2 randomized trials) comprising 20, 291 patients (mean age 71.3±3.0 years; 74.6% men) were included. Patients in the open-cell stent group had a statistically significant lower risk of restenosis ⩾40% (OR 0.42, 95% CI 0.19 to 0.92; I2=0%) and ⩾70% (OR 0.23, 95% CI 0.10 to 0.52; I2=0%) at a mean follow-up of 24 months. No statistically significant differences were identified for periprocedural stroke, TIA, new ischemic lesions, MI, hemodynamic depression, or death within 30 days after CAS. Sensitivity analysis of the 2 randomized controlled trials only did not point to any significant differences either. CONCLUSION: Use of open-cell stent design in CAS is associated with a decreased risk for restenosis when compared to the closed-cell stent, without significant differences in periprocedural outcomes.