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1. Metabolic biochemical models of N ₂ fixation for sulfide oxidizers, methanogens, and methanotrophs

   https://doi.org/10.1128/msystems.00748-25  

   Gao, Meng; Berberich, Megan E; Brown, Reid; Costello, David M; Cotner, James B; Damashek, Julian; Kittu, Leila Richards; Pastor, Ada; Fulweiler, Robinson W; Scott, J Thad; et al (October 2025, mSystems)

   Fahimipour, Ashkaan K (Ed.)

   ABSTRACT Dinitrogen (N₂) fixation provides bioavailable nitrogen to the biosphere. However, in some habitats (e.g., sediments), the metabolic pathways of organisms carrying out N₂fixation are unclear. We present metabolic models representing various chemotrophic N₂fixers, which simulate potential pathways of electron transport and energy flow, resulting in predictions of whole-cell stoichiometries. By balancing mass, electrons, and energy for metabolic half-reactions, we quantify the electron usage for nine N₂fixers. Our results demonstrate that all modeled organisms fix sufficient N₂for growth. Aerobic organisms allocate more electrons to N₂fixation and growth, yielding more biomass and fixing more N₂, while methanogens using acetate and organisms using sulfate allocate fewer electrons. This work can be applied to investigate the depth distribution of N₂fixers based on nutrient availability, complementing field measurements of biogeochemical processes and microbial communities.IMPORTANCEN₂fixation is an important process in the global N cycle. Researchers have developed models for heterotrophic and photoautotrophic N₂fixers, but there is a lack of modeling studies on chemoautotrophic N₂fixers. Here, we built nine biochemical models for different chemoautotrophic N₂fixers by combining different types of half-chemical reactions. We include three sulfide oxidizers using different electron acceptors (O₂, NO₃⁻, and Fe³⁺), contributing to the sulfur, nitrogen, and iron cycles in the sediment. We have two methanogens using different substrates (H₂and acetate) and four methanotrophs using different electron acceptors (O₂, NO₃⁻, Fe³⁺, and SO₄²⁻). By modeling these methane producers and users in the sediment and their N₂-fixing metabolic pathways, our work can provide insight for future carbon cycle studies. This study outlines various metabolic pathways that can facilitate N₂fixation, with implications for where in the environment they might occur. 

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2. Electrodeposition Parameters Dramatically Influence the Morphology, Stability, and Performance of n‐Si/Pt Light‐Addressable Electrochemical Sensors

   https://doi.org/10.1002/celc.202300400  

   Hernandez, Jocelyn_B; Epright, Zackary_D; Terrero_Rodríguez, Irina_M; O'Neil, Glen_D (November 2023, ChemElectroChem)

   Abstract Light addressable electrochemical (LAE) sensors have seen great utility in the past several years because they enable multiple localized electrochemical measurements to be performed on a single macroscopic electrode, opening up applications in imaging, biosensing, surface patterning, and multiplexing. In this study, we investigated the effects of electrodeposition on the formation of LAE sensors formed between n‐Si and electrodeposited Pt. We prepared sensors by electrodepositing Pt onto freshly‐etched n‐Si under a variety of conditions, varying the Pt precursor concentration, electrodeposition time, supporting electrolyte, and potential waveform. We characterized the sensors using a combination of atomic force microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. This study shows that the electrodeposition parameters have a dramatic impact on the morphology of the electrodeposited surfaces, sensor stability, and sensitivity towards H₂O₂. Specifically, we observed that continuous Pt films prepared with a higher Pt precursor concentration were more stable and had better linearity, higher sensitivity, and broader dynamic range than those prepared with a lower Pt precursor concentration. The stability and increased H₂O₂sensing performance correlate strongly with an increase in the Pt islands which make up the film. These data highlight that the morphology of the metal in semiconductor/metal junction LAE sensors has an impact on important performance metrics like stability and sensitivity. They also demonstrate the need for semiconductor/metal LAE sensors to be studied using micro‐ and nanoscale imaging techniques in order to more deeply understand their performance characteristics. 

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3. On the Range Assignment in Wireless Sensor Networks for Minimizing the Coverage-Connectivity Cost

   https://doi.org/10.1145/3457408  

   Das, Sajal K; Kapelko, Rafał (November 2021, ACM Transactions on Sensor Networks)

   This article deals with reliable and unreliable mobile sensors having identical sensing radiusr, communication radiusR, provided thatr≤Rand initially randomly deployedon the planeby dropping them from an aircraft according to general random process. The sensors have to move from their initial random positions to the final destinations to provide greedy pathk₁-coverage simultaneously withk₂-connectivity. In particular, we are interested in assigning the sensing radiusrand communication radiusRto minimizethe time requiredandthe energy consumptionof transportation cost for sensors to provide the desiredk₁-coverage withk₂-connectivity. We prove that for both of these optimization problems, the optimal solution is to assign the sensing radius equal tor=k₁||E[S]||/2 and the communication radiusR=k₂||E[S]||/2, where ||E[S]|| is the characteristic of general random process according to which the sensors are deployed. Whenr<k₁||E[S]||/2 orR<k₂||E[S]||/ 2, and sensors are reliable, we discover and explainthe sharp increasein the time required and the energy consumption in transportation cost to ensure the desiredk₁-coverage withk₂-connectivity. 

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4. Freestanding BaTiO ₃ ‐Au Vertically Aligned Nanocomposite toward Flexible Multi‐Sensing Platform

   https://doi.org/10.1002/adfm.202418004  

   Tsai, Benson_Kunhung; Huang, Jialong; Yu, Ya‐Ching; Lee, Meng_Hao; Stegman, Benjamin_Thomas; Flores, Emiliano_Joseph; Tong, Patrick_Zhang; Xu, Ke; Zhou, Shiyu; Shen, Jianan; et al (January 2025, Advanced Functional Materials)

   Abstract Flexible and wearable sensors show enormous potential for personalized healthcare devices by real‐time monitoring of an individual's health. Typically, a single functional material is selected for one sensor to sense a particular physical signal while multiple materials will be selected for multi‐mode sensing. Vertically aligned nanocomposites (VANs) have recently demonstrated various material combinations and novel coupled multifunctionalities that are hard to achieve in any single‐phase material alone, including multiphase multiferroics, magneto‐optic coupling, and strong magnetic and optical anisotropy. Integrating these novel VANs into wearable sensors shows enormous potential in multi‐mode sensing owing to their multifunctional nature. In this work, the transfer of VANs onto polydimethylsiloxane as a novel flexible chemical and pressure sensor is demonstrated. For this demonstration, the classical BaTiO₃‐Au VAN with combined plasmonic and piezoelectric properties is used to demonstrate a multi‐sensing mechanism. A thin water‐soluble buffer of Sr₃Al₂O₆serves as a buffer layer for the epitaxial growth and transfer process. The electrical output based on the piezoelectric responses and identifying 4‐mercaptobenzoic acid by surface‐enhanced Raman spectroscopy reveal great potential for free‐standing VANs in a wearable multifunctional sensing platform. 

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5. The estimation of gross oxygen production and community respiration from autonomous time‐series measurements in the oligotrophic ocean

   https://doi.org/10.1002/lom3.10340  

   Barone, Benedetto; Nicholson, David; Ferrón, Sara; Firing, Eric; Karl, David (November 2019, Limnology and Oceanography: Methods)

   Abstract Diel variations in oxygen concentration have been extensively used to estimate rates of photosynthesis and respiration in productive freshwater and marine ecosystems. Recent improvements in optical oxygen sensors now enable us to use the same approach to estimate metabolic rates in the oligotrophic waters that cover most of the global ocean and for measurements collected by autonomous underwater vehicles. By building on previous methods, we propose a procedure to estimate photosynthesis and respiration from vertically resolved diel measurements of oxygen concentration. This procedure involves isolating the oxygen variation due to biological processes from the variation due to physical processes, and calculating metabolic rates from biogenic oxygen changes using linear least squares analysis. We tested our method on underwater glider observations from the surface layer of the North Pacific Subtropical Gyre where we estimated rates of gross oxygen production and community respiration both averaging 1.0 mmol O₂m⁻³d⁻¹, consistent with previous estimates from the same environment. Method uncertainty was computed as the standard deviation of the fitted parameters and averaged 0.6 and 0.5 mmol O₂m⁻³d⁻¹for oxygen production and respiration, respectively. The variability of metabolic rates was larger than this uncertainty and we were able to discern covariation in the biological production and consumption of oxygen. The proposed method resolved variability on time scales of approximately 1 week. This resolution can be improved in several ways including by measuring turbulent mixing, increasing the number of measurements in the surface ocean, and adopting a Lagrangian approach during data collection. 

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