Optimization of Dynamic Surface Plastic Deformation in Machining
Machining by surface plastic deformation in granulated media is investigated. The process is optimized in terms of fluctuation of the strain rate.
42 ENGINEERING↗
SEARCH · Engineering Papers
Results for “Strain engineering”
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Data for "Metabolic Engineering Strategies to Produce Medium-Chain Oleochemicals via Acyl-ACP:CoA Transacylase Activity"
Microbial lipid metabolism is an attractive route for producing oleochemicals. The predominant strategy centers on heterologous thioesterases to synthesize desired chain-length fatty acids. To convert acids to oleochemicals (e.g., fatty alcohols, ketones), the narrowed fatty acid pool needs to be reactivated as coenzyme A thioesters at cost of one ATP per reactivation – an expense that could be saved if the acyl-chain was directly transferred from ACP- to CoA-thioester. Here, we demonstrate such an alternative acyl-transferase strategy by heterologous expression of PhaG, an enzyme first identified in Pseudomonads, that transfers 3-hydroxy acyl-chains between acyl-carrier protein and coenzyme A thioester forms for creating polyhydroxyalkanoate monomers. We use it to create a pool of acyl-CoA’s that can be redirected to oleochemical products. Through bioprospecting, mutagenesis, and metabolic engineering, we develop three strains of Escherichia coli capable of producing over 1 g/L of medium-chain free fatty acids, fatty alcohols, and methyl ketones.
Bioproducts↗
Electrons to Molecules by Engineering and Evolution: Biological Upgrading of Formate by Cupriavidus necator
Waste carbon from industrial point sources can be captured, stored, and/or transformed using electrochemical conversion or "electrons to molecules" technologies using low-cost renewable electricity. One such process involves electrocatalytic reduction of CO2 to generate formate/formic acid, a C1 carboxylic acid. Formate is a promising potential feedstock for microbial upgrading, as it is water soluble and can be consumed as the sole source of carbon and energy by some microbial species, such as the soil bacterium Cupriavidus necator. Here we will present progress toward improving C. necator as a host for biological conversion of formate to value-added products. Using the power of adaptive laboratory evolution, we were able to isolate mutants of C. necator with significantly faster growth rates on formate. We then sequenced the genomes of these strains, elucidated the metabolic role of the mutations we found, and then used these insights to build rationally engineered strains that outperform even the best evolved isolates. These results highlight the utility of "genome streamlining" as a route for generating platform strains with potential industrial applications.
adaptive laboratory evolution↗
Cas9-Based Metabolic Engineering of Issatchenkia orientalis for Enhanced Utilization of Cellulosic Hydrolysates
Issatchenkia orientalis, exhibiting high tolerance against harsh environmental conditions, is a promising metabolic engineering host for producing fuels and chemicals from cellulosic hydrolysates containing fermentation inhibitors under acidic conditions. Although genetic tools for I. orientalis exist, they require auxotrophic mutants so that the selection of a host strain is limited. We developed a drug resistance gene (cloNAT)-based genome-editing method for engineering any I. orientalis strains and engineered I. orientalis strains isolated from various sources for xylose fermentation. Specifically, xylose reductase, xylitol dehydrogenase, and xylulokinase from Scheffersomyces stipitis were integrated into an intended chromosomal locus in four I. orientalis strains (SD108, IO21, IO45, and IO46) through Cas9-based genome editing. Furthermore, the resulting strains (SD108X, IO21X, IO45X, and IO46X) efficiently produced ethanol from cellulosic and hemicellulosic hydrolysates even though the pH adjustment and nitrogen source were not provided. As they presented different fermenting capacities, selection of a host I. orientalis strain was crucial for producing fuels and chemicals using cellulosic hydrolysates.
09 BIOMASS FUELS↗
Data for L-Malic Acid Production from Xylose by Engineered Saccharomyces cerevisiae
L-malic acid is widely used in the food, chemical, and pharmaceutical industries. Here, we report on production of malic acid from xylose, the second most abundant sugar in lignocellulosic hydrolysates, by engineered Saccharomyces cerevisiae . To enable malic acid production in a xylose-assimilating S. cerevisiae , we overexpressed PYC1 and PYC2, coding for pyruvate carboxylases, a truncated MDH3 coding for malate dehydrogenase, and SpMAE1, coding for a Schizosaccharomyces pombe malate transporter. Additionally, both the ethanol- and glycerol-producing pathways were blocked to enhance malic acid production. The resulting strain produced malic acid from both glucose and xylose, but it produced much higher titers of malic acid from xylose than glucose. Interestingly, the engineered strain had higher malic acid yield from lower concentrations (10 g L‒1) of xylose, with no ethanol production, than from higher xylose concentrations (20 and 40 g L‒1). As such, a fed-batch culture maintaining xylose concentrations at low levels was conducted and 61.2 g L‒1 of malic acid was produced, with a productivity of 0.32 g L‒1 h. These results represent successful engineering of S. cerevisiae for the production of malic acid from xylose, confirming that that xylose offers the efficient production of various biofuels and chemicals by engineered S. cerevisiae .
Conversion↗
L–malic acid production from xylose by engineered Saccharomyces cerevisiae
L-malic acid is widely used in the food, chemical, and pharmaceutical industries. Here, we report on production of malic acid from xylose, the second most abundant sugar in lignocellulosic hydrolysates, by engineered Saccharomyces cerevisiae. To enable malic acid production in a xylose-assimilating S. cerevisiae, we overexpressed PYC1 and PYC2, coding for pyruvate carboxylases, a truncated MDH3 coding for malate dehydrogenase, and SpMAE1, coding for a Schizosaccharomyces pombe malate transporter. Additionally, both the ethanol and glycerol-producing pathways were blocked to enhance malic acid production. The resulting strain produced malic acid from both glucose and xylose, but it produced much higher titers of malic acid from xylose than glucose. Interestingly, the engineered strain had higher malic acid yield from lower concentrations (10 g L –1 ) of xylose, with no ethanol production, than from higher xylose concentrations (20 and 40 g L –1 ). As such, a fed-batch culture maintaining xylose concentrations at low levels was conducted and 61.2 g L –1 of malic acid was produced, with a productivity of 0.32 g L –1 h. Furthermore, these results represent successful engineering of S. cerevisiae for the production of malic acid from xylose, confirming that that xylose offers the efficient production of various biofuels and chemicals by engineered S. cerevisiae.
59 BASIC BIOLOGICAL SCIENCES↗
A New Residual Strain Mapping Program Using Energy Dispersive X-Ray Diffraction at the Advanced Photon Source
Here, the ability to non-destructively map the residual strain field inside an engineering component is important for predicting its fatigue life or developing processing methods to prevent failure or enhance performance. In this paper, we describe a new residual strain mapping program at the Advanced Photon Source, Argonne National Laboratory. The new program is based on energy dispersive x-ray diffraction (EDXRD). It is capable of non-destructively penetrating a several- cm thick polycrystalline sample fabricated from engineering alloys using high-energy x-rays and measuring the residual strain field with mm or better spatial resolution and approximately ±1 x 10 -4 strain resolution. A multi-element detector array is employed to measure multiple strain components simultaneously. The residual strain mapping setup is augmented with a high-energy tomography capability, allowing precise alignment of the material volume of interest for residual strain mapping and providing a complementary view of the structure to understand the measured strain field. These measurement capabilities are demonstrated using several strain mapping examples ranging from polycrystalline structural alloys to biological materials. We also provide some guidance for the future users of the program for a successful residual strain mapping experiment. We are expanding the capabilities of the new setup with various in situ capabilities including thermo-mechanical loading.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Experimental Investigation of Vibratory Stresses in a Concentric-Ring Direct-Air-Cycle Nuclear Fuel Element
Preliminary tests made by the General Electric Company indicated that aerodynamic loads might cause large enough distortions in the thin sheet-metal rings of a nuclear fuel element to result in structural failure. The magnitude of the distortions in a test fuel element was determined from strains measured with airflow conditions simulating those expected during engine operation. The measured vibratory strains were low enough to indicate the improbability of failure by fatigue. A conservative estimate of the radial deflection that accompanied peak strains in the outer ring was +0.0006 inch.
Chiarito, Patrick T.↗
Procedures for experimental measurement and theoretical analysis of large plastic deformations
Theoretical equations are derived and analytical procedures are presented for the interpretation of experimental measurements of large plastic strains in the surface of a plate. Orthogonal gage lengths established on the metal surface are measured before and after deformation. The change in orthogonality after deformation is also measured. Equations yield the principal strains, deviatoric stresses in the absence of surface friction forces, true stresses if the stress normal to the surface is known, and the orientation angle between the deformed gage line and the principal stress-strain axes. Errors in the measurement of nominal strains greater than 3 percent are within engineering accuracy. Applications suggested for this strain measurement system include the large-strain-stress analysis of impact test models, burst tests of spherical or cylindrical pressure vessels, and to augment small-strain instrumentation tests where large strains are anticipated.
Morris, R. E.↗
Development of a rotary instrumentation system, phase 2
A rotary instrumentation system which consists of ruggedized miniature telemetry transmitters installed on the rotating shaft of a gas turbine engine to telemeter the outputs of sensors (strain gages, thermocouples, etc.) on rotating engine components was designed. A small prototype system, which demonstrates the capabilities of performing in the intended environment and demonstrates that the system is expandable to handle about 100 data channels was developed.
Adler, A.↗
Evaluation results of the 700 deg C Chinese strain gauges
Gauges fabricated from specially developed Fe-Cr-Al-V-Ti-Y alloy wire in the Republic of China were evaluated for use in static strain measurement of hot gas turbine engines. Gauge factor variation with temperature, apparent strain, and drift were included. Results of gauge factor versus temperature tests show gauge factor decreasing with increasing temperature. The average slope is -3-1/2 percent/100 K, with an uncertainty band of + or - 8 percent. Values of room temperature gauge factor for the Chinese and Kanthal A-1 gauges averaged 2.73 and 2.12, respectively. The room temperature gauge factor of the Chinese gauges was specified to be 2.62. The apparent strain data for both the Chinese alloy and Kanthal A-1 showed large cycle to cycle nonrepeatability. All apparent strain curves had a similar S-shape, first going negative and then rising to positive value with increasing temperatures. The mean curve for the Chinese gauges between room temperature and 100 K had a total apparent strain of 1500 microstrain. The equivalent value for Kanthal A-1 was about 9000 microstrain. Drift tests at 950 K for 50 hr show an average drift rate of about -9 microstrain/hr. Short-term (1 hr) rates are higher, averaging about -40 microstrain for the first hour. In the temperature range 700 to 870 K, however, short-term drift rates can be as high as 1700 microstrain for the first hour. Therefore, static strain measurements in this temperature range should be avoided.
Hobart, H. F.↗
Design Principles in Engineering of Multigrain Nanocatalysts via Multiscale Electronic Structure Characterization
Engineering grain boundary (GB) strain provides a promising pathway to tune the catalytic properties of nanocrystals. However, structural heterogeneity from random grain orientation and geometry has limited clear structure–property correlations. Here, we utilize a multigrain Co3O4/Mn3O4 core/shell nanocrystal platform as a model system to systematically investigate how geometric misfit strain at GBs serves as catalytically active sites for the oxygen reduction reaction. Through precise subnanometer-level control over grain morphology and by integrating multiscale electronic structure characterization, we identify the electronic structural signature of GB defects and establish a direct correlation between localized strain fields and modified electronic states. Strain modulation at GBs alters the eg orbital energy levels, with elongation along the z-axis combined with shear strain stabilizing the eg states, in contrast to the destabilization observed under pure shear strain. This stabilization mechanism enhances the electrocatalytic activity and selectivity of strained GBs compared with strain-relaxed grain surfaces. Furthermore, we reveal that GBs exhibit a radial strain gradient, producing a spatial energy shift that further modulates local electronic structures, as resolved through the classification of electron energy loss spectroscopy data. Together, these findings demonstrate that geometric misfit strain enables precise tuning of grain geometry and the resulting electronic structures, offering a robust strategy for engineering next-generation nanocatalysts.
Cho, Min Gee↗
Susceptibility to quantum dot induced lung inflammation differs widely among the Collaborative Cross founder mouse strains
Quantum dots (QDs) are engineered semiconductor nanoparticles with unique physicochemical properties that make them potentially useful in clinical, research and industrial settings. However, a growing body of evidence indicates that like other engineered nanomaterials, QDs have the potential to be respiratory hazards, especially in the context of the manufacture of QDs and products containing them, as well as exposures to consumers using these products. The overall goal of this study was to investigate the role of mouse strain in determining susceptibility to QD-induced pulmonary inflammation and toxicity. Male mice from 8 genetically diverse inbred strains (the Collaborative Cross founder strains) were exposed to CdSe–ZnS core–shell QDs stabilized with an amphiphilic polymer. QD treatment resulted in significant increases in the percentage of neutrophils and levels of cytokines present in bronchoalveolar lavage fluid (BALF) obtained from NOD/ShiLtJ and NZO/HlLtJ mice relative to their saline (Sal) treated controls. Cadmium measurements in lung tissue indicated strain-dependent differences in disposition of QDs in the lung. Total glutathione levels in lung tissue were significantly correlated with percent neutrophils in BALF as well as with lung tissue Cd levels. Our findings indicate that QD-induced acute lung inflammation is mouse strain dependent, that it is heritable, and that the choice of mouse strain is an important consideration in planning QD toxicity studies. These data also suggest that formal genetic analyses using additional strains or recombinant inbred strains from these mice could be useful for discovering potential QD-induced inflammation susceptibility loci. - Highlights: • Quantum dot acute lung inflammation was evaluated in a multi-strain mouse model. • QD disposition differed across 8 Collaborative Cross (CC) founder strains. • Neutrophil and cytokine levels in BALF were also mouse strain dependent. • NOD/ShiLtJ, NZO/HlLtJ, and A/J were more sensitive to QDs than C57BL/6J mice. • The cytokines KC and Mip1α were strongly correlated with Cd and BALF neutrophils.
60 APPLIED LIFE SCIENCES↗
Generation of Pseudomonas putida KT2440 Strains with Efficient Utilization of Xylose and Galactose via Adaptive Laboratory Evolution
While Pseudomonas putida KT2440 has great potential for biomass-converting processes, its inability to utilize the biomass abundant sugars xylose and galactose has limited its applications. Here, in this study, we utilized Adaptive Laboratory Evolution (ALE) to optimize engineered KT2440 with heterologous expression of xylD encoding xylonate dehydratase from Caulobacter crescentus and galETKM encoding UDP-glucose 4-epimerase, galactose-1-phosphate uridylyltransferase, galactokinase, and galactose-1-epimerase from Escherichia coli K-12 MG1655. Poor starting strain growth (<0.1 h –1 or none) was evolutionarily optimized to rates of up to 0.25 h –1 on xylose and 0.52 h –1 on galactose. Whole-genome sequencing, transcriptomic analysis, and growth screens revealed significant roles of kguT encoding a 2-ketogluconate operon repressor and 2-ketogluconate transporter, and gtsABCD encoding an ATP-binding cassette (ABC) sugar transporting system in xylose and galactose growth conditions, respectively. Finally, we expressed the heterologous indigoidine production pathway in the evolved and unevolved engineered strains and successfully produced 3.2 g/L and 2.2 g/L from 10 g/L of either xylose or galactose in the evolved strains whereas the unevolved strains did not produce any detectable product. Thus, the generated KT2440 strains have the potential for broad application as optimized platform chassis to develop efficient microorganism-based biomass-utilizing bioprocesses.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
13 C Metabolic Flux Analysis for Systematic Metabolic Engineering of S. cerevisiae for Overproduction of Fatty Acids
Efficient redirection of microbial metabolism into the abundant production of desired bioproducts remains non-trivial. Here, we used flux-based modeling approaches to improve yields of fatty acids in Saccharomyces cerevisiae. We combined 13 C labeling data with comprehensive genome-scale models to shed light onto microbial metabolism and improve metabolic engineering efforts. We concentrated on studying the balance of acetyl-CoA, a precursor metabolite for the biosynthesis of fatty acids. A genome-wide acetyl-CoA balance study showed ATP citrate lyase from Yarrowia lipolytica as a robust source of cytoplasmic acetyl-CoA and malate synthase as a desirable target for downregulation in terms of acetyl-CoA consumption. These genetic modifications were applied to S. cerevisiae WRY2, a strain that is capable of producing 460 mg/L of free fatty acids. With the addition of ATP citrate lyase and downregulation of malate synthase, the engineered strain produced 26% more free fatty acids. Further increases in free fatty acid production of 33% were obtained by knocking out the cytoplasmic glycerol-3-phosphate dehydrogenase, which flux analysis had shown was competing for carbon flux upstream with the carbon flux through the acetyl-CoA production pathway in the cytoplasm. In total, the genetic interventions applied in this work increased fatty acid production by ~70%.
-omics data↗
Defect-Enabled Phase Programming of Transition Metal Dichalcogenide Monolayers
The ability to tune the local electronic transport properties of group VI transition metal dichalcogenide (TMD) monolayers by strain-induced structural phase transformations (“phase programming”) has stimulated much interest in the potential applications of such layers as ultrathin programmable and dynamically switchable nanoelectronics components. In this manuscript, we propose a new approach toward controlling TMD monolayer phases by employing macroscopic in-plane strains to amplify heterogeneous strains arising from tailored, spatially extended defects within the monolayer. Furthermore, the efficacy of our proposed approach is demonstrated via numerical simulations of emerging domains localized around arrays of holes, grain boundaries, and compositional heterointerfaces. Quantitative relations between the macroscopic strains required, spatial resolution of domain patterns, and defect configurations are developed. In particular, the introduction of arrays of holes is identified as the most feasible phase programming route.
2D materials↗
Engineering and Two-Stage Evolution of a Lignocellulosic Hydrolysate-Tolerant Saccharomyces cerevisiae Strain for Anaerobic Fermentation of Xylose from AFEX Pretreated Corn Stover
The inability of the yeast Saccharomyces cerevisiae to ferment xylose effectively under anaerobic conditions is a major barrier to economical production of lignocellulosic biofuels. Although genetic approaches have enabled engineering of S. cerevisiae to convert xylose efficiently into ethanol in defined lab medium, few strains are able to ferment xylose from lignocellulosic hydrolysates in the absence of oxygen. This limited xylose conversion is believed to result from small molecules generated during biomass pretreatment and hydrolysis, which induce cellular stress and impair metabolism. Here, we describe the development of a xylose-fermenting S. cerevisiae strain with tolerance to a range of pretreated and hydrolyzed lignocellulose, including Ammonia Fiber Expansion (AFEX)-pretreated corn stover hydrolysate (ACSH). We genetically engineered a hydrolysate-resistant yeast strain with bacterial xylose isomerase and then applied two separate stages of aerobic and anaerobic directed evolution. The emergent S. cerevisiae strain rapidly converted xylose from lab medium and ACSH to ethanol under strict anaerobic conditions. Metabolomic, genetic and biochemical analyses suggested that a missense mutation in GRE3, which was acquired during the anaerobic evolution, contributed toward improved xylose conversion by reducing intracellular production of xylitol, an inhibitor of xylose isomerase. These results validate our combinatorial approach, which utilized phenotypic strain selection, rational engineering and directed evolution for the generation of a robust S. cerevisiae strain with the ability to ferment xylose anaerobically from ACSH.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Densely Aligned Graphene Nanoribbon Arrays and Bandgap Engineering
Graphene has attracted great interest for future electronics due to its high mobility and high thermal conductivity. However, a two-dimensional graphene sheet behaves like a metal, lacking a bandgap needed for the key devices components such as field effect transistors (FETs) in digital electronics. It has been shown that, partly due to quantum confinement, graphene nanoribbons (GNRs) with ~2 nm width can open up sufficient bandgaps and evolve into semiconductors to exhibit high on/off ratios useful for FETs. However, a challenging problem has been that, such ultra-narrow GNRs (~2 nm) are difficult to fabricate, especially for GNRs with smooth edges throughout the ribbon length. Despite high on/off ratios, these GNRs show very low mobility and low on-state conductance due to dominant scattering effects by imperfections and disorders at the edges. Wider GNRs (>5 nm) show higher mobility, higher conductance but smaller bandgaps and low on/off ratios undesirable for FET applications. It is highly desirable to open up bandgaps in graphene or increase the bandgaps in wide GNRs to afford graphene based semiconductors for high performance (high on-state current and high on/off ratio) electronics. Large scale ordering and dense packing of such GNRs in parallel are also needed for device integration but have also been challenging thus far. It has been shown theoretically that uniaxial strains can be applied to a GNR to engineer its bandgap. The underlying physics is that under uniaxial strain, the Dirac point moves due to stretched C-C bonds, leading to an increase in the bandgap of armchair GNRs by up to 50% of its original bandgap (i.e. bandgap at zero strain). For zigzag GNRs, due to the existence of the edge states, changes of bandgap are smaller under uniaxial strain and can be increased by ~30%. This work proposes a novel approach to the fabrication of densely aligned graphene nanoribbons with highly smooth edges afforded by anisotropic etching and uniaxial strain for bandgap engineering of GNRs towards high on/off ratio and high on-state current GNR devices. First, we will develop a novel approach for the fabrication of high density GNR arrays (pitch <50 nm, tunable down to 30nm) with pre-defined edge orientation and smooth edges using a free standing nano-mask derived from diblock copolymer assembly for patterning of graphene sheets. Anisotropic graphene edges will be developed to afford smooth edges along crystallographic lattice directions. Then, we will fabricate GNR devices on flexible substrates and apply uniaxial strain to engineer the bandgap of the GNRs. The bandgap of GNRs could be increased by up to 50% under uniaxial strain according to theoretical calculations and will be investigated through electrical transport measurements. Micro-Raman spectroscopy of single GNRs and parallel arrays will be used to probe and quantify the uniaxial strain. Electrical measurements will be used to probe the on/off ratio of GNR FET devices and confirm the bandgap tuning effects. Finally, we plan to use dense parallel arrays of GNRs to demonstrate strained GNR field effect transistors with high on/off ratios and high on-state current, and compare strained GNR FETs with carbon nanotube and Si based field effect transistor (FET) devices.
42 ENGINEERING↗