CO2 is converted into biomass almost solely by the enzyme rubisco. The poor carboxylation properties of plant rubiscos have led to efforts that made it the most kinetically characterized enzyme, yet these studies focused on < 5% of its natural diversity. Here, we searched for fast‐carboxylating variants by systematically mining genomic and metagenomic data. Approximately 33,000 unique rubisco sequences were identified and clustered into ≈ 1,000 similarity groups. We then synthesized, purified, and biochemically tested the carboxylation rates of 143 representatives, spanning all clusters of form‐II and form‐II/III rubiscos. Most variants (> 100) were active in vitro, with the fastest having a turnover number of 22 ± 1 s−1—sixfold faster than the median plant rubisco and nearly twofold faster than the fastest measured rubisco to date. Unlike rubiscos from plants and cyanobacteria, the fastest variants discovered here are homodimers and exhibit a much simpler folding and activation kinetics. Our pipeline can be utilized to explore the kinetic space of other enzymes of interest, allowing us to get a better view of the biosynthetic potential of the biosphere.

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In this study, micro/nanoscaled hierarchical hybrid coatings containing titanium (Ti) phosphate and Ti oxide have been fabricated with the aim of promoting osseointegration of Ti-based implants. Three representative surface coatings, namely, micro/nanograss Ti (P-G-Ti), micro/nanoclump Ti, (P-C-Ti), and micro/nanorod Ti (P-R-Ti), have been produced. In-depth investigations into the coating surface morphology, topography, chemical composition, and the surface/cell interaction have been carried out using scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, X-ray diffraction, contact-angle measurement, and protein adsorption assay. In addition, in vitro performance of the coating (cell proliferation, adhesion, and differentiation) has been evaluated using rat bone marrow stromal cells (BMSCs), and in vivo assessments have been carried out based on a rat tibia implantation model. All the hybrid coating modified implants demonstrated enhanced protein adsorption and BMSC viability, adhesion and differentiation, with P-G-Ti showing the best bioactivity among all samples. Subsequent i n vivo osseointegration tests confirmed that P-G-Ti has induced a much stronger interfacial bonding with the host tissue, indicated by the 2-fold increase in the ultimate shear strength and over 6-fold increase in the maximum push-out force compared to unmodified Ti implants. The state-of-the-art coating technology proposed for Ti-based implants in this study holds great potential in advancing medical devices for next-generation healthcare technology.

The proper selection of electrical contact materials is one of the critical steps in designing a metal contact microelectromechanical system ͑MEMS͒ switch. Ideally, the contact should have both very low contact resistance and high wear resistance. Unfortunately this combination cannot be easily achieved with the contact materials currently used in macroswitches because the available contact force in microswitches is generally insufficient ͑less than 1 mN͒ to break through nonconductive surface layers. As a step in the materials selection process, three noble metals, platinum ͑Pt͒, rhodium ͑Rh͒, ruthenium ͑Ru͒, and their alloys with gold ͑Au͒ were deposited as thin films on silicon ͑Si͒ substrates. The contact resistances of these materials and their evolution with cycling were measured using a specially developed scanning probe microscope test station. These results were then compared to measurements of material hardness and resistivity. The initial contact resistances of the noble metals alloyed with Au are roughly proportional to their resistivities. Measurements of contact resistance during cycling of different metal films were made under a contact force of 200-250 N in a room air environment. It was found that the contact resistance increases with cycling for alloy films with a low concentration of gold due to the buildup of contamination on the contact. However, for alloy films with a high gold content, the contact resistance increase due to contamination is insignificant up to 10 8 cycles. These observations suggest that Rh, Ru, and Pt and their gold alloys of low gold content are prone to contamination failure as contact materials in MEMS switches.

Lithium–sulfur (Li–S) batteries are promising next-generation energy storage devices because of their high energy density of 2600 Wh kg–1. Efficient immobilization and fast conversion of soluble lithium polysulfide intermediates (LiPSs) are crucial to the electrochemical performance of Li–S batteries. Herein, we report a novel strategy to simultaneously achieve large capacity, high rate capability, and long cycle life by utilizing mesoporous niobium nitride microspheres/N-doped graphene nanosheets (NbN@NG) hybrids as multifunctional host materials for sulfur cathodes. The mesoporous NbN microspheres chemically immobilize LiPSs via Nb–S chemical bonding and catalytically promote conversion of LiPSs into insoluble Li2S resulting in enhanced redox reaction kinetics. Moreover, the highly conductive NbN and N-doped graphene nanosheets provide rapid electron transport and consequently, the S/NbN@NG cathode demonstrates a large capacity of 948 mAh g–1 at 1C (1C = 1650 mA g–1), high rate capability of 739 mAh g–1 at 5C, and excellent cycle stability with a capacity decay of 0.09% per cycle for over 400 cycles. The results described here provide insights into the design of multifunctional host materials for high-performance Li–S batteries.

In this paper we present a 3D nonlinear dynamic model which describes the transient mechanical analysis of an ohmic contact RF MEMS switch, using finite element analysis in combination with the finite difference method. The model includes real switch geometry, electrostatic actuation, the two-dimensional non-uniform squeeze-film damping effect, the adherence force, and a nonlinear spring to model the interaction between the contact tip and the drain. The ambient gas in the package is assumed to act as an ideal and isothermal fluid which is modeled using the Reynolds squeeze-film equation which includes compressibility and slip flow. A nonlinear contact model has been used for modeling contact between the microswitch tip and the drain electrode during loading. The Johnson-Kendall-Roberts (JKR) contact model is utilized to calculate the adherence force during unloading. The developed model has been used to simulate the overall dynamic behavior of the MEMS switches including the switching speed, impact force and contact bounce as influenced by actuation voltage, damping, materials properties and geometry. Meanwhile, based on a simple undamped spring-mass system, a dual voltage-pulse actuation scheme, consisting of actuation voltage (V a ), actuation time (t a ), holding voltage (V h ) and turn-on time (t on ), has been developed to improve the dynamic response of the microswitch. It is shown that the bouncing of the switch after initial contact can be eliminated and the impact force during contact can be minimized while maintaining a fast close time by using this open-loop control approach. It is also found that the dynamics of the switch are sensitive to the variations of the shape of the dual pulse scheme. This result suggests that this method may not be as effective as expected if the switch parameters such as threshold voltage, fundamental frequencies, etc. deviate too much from the design parameters. However, it is shown that the dynamic performance may be improved by increasing the damping force. The simulation results obtained from this dynamic model are confirmed by experimental measurement of the RF MEMS switches which were developed at the Northeastern University. It is anticipated that the simulation method can serve as a design tool for dynamic optimization of the microswitch. In addition, the approach of tailoring actuation voltage and the utilization of squeeze-film damping may provide further improvements in the operation of RF MEMS switches.

Severe injury induces detrimental changes in immune function, often leaving the host highly susceptible to developing life-threatening opportunistic infections. Advances in our understanding of how injury influences host immune responses suggest that injury causes a phenotypic imbalance in the regulation of Th1- and Th2-type immune responses. We report in this study, using a TCR transgenic CD4+ T cell adoptive transfer approach, that injury skews T cell responses toward increased Th2-type reactivity in vivo without substantially limiting Ag-driven CD4+ T cell expansion. The increased Th2-type response did not occur unless injured mice were immunized with specific Ag, suggesting that the phenotypic switch is Ag dependent. These findings establish that severe injury induces fundamental changes in the induction of Ag-specific CD4+ Th cell responses favoring the development of Th2-type immune reactivity in vivo.

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