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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Preparation and characterization of spinel nickel ferrite obtained by the soft mechanochemically assisted synthesis

Graphical abstract: Display Omitted Highlights: ► NiFe{sub 2}O{sub 4} has been prepared by a soft mechanochemical route from mixture of powders. ► The spinel phase formation was completed after 25 h. ► The synthesized ferrites have a crystallite size of about 25 and 15 nm. ► Based on Raman research is observed five first-order Raman active modes. ► We were able to estimate the degree of inversion at most 0.82 and 0.66. -- Abstract: Nickel ferrite, NiFe{sub 2}O{sub 4} has been prepared by a soft mechanochemical route from mixture of (1) Ni(OH){sub 2} and α-Fe{sub 2}O{sub 3} and (2) Ni(OH){sub 2} and Fe(OH){sub 3} powders in a planetary ball mill for varying duration. Soft mechanochemical reaction leading to formation of the NiFe{sub 2}O{sub 4} spinel phase was followed by X-ray diffraction, Raman and infrared spectroscopy, TGA, scanning and transmission microscopy. The spinel phase formation was first observed after 4 h of milling and its formation was completed after 25 h in the both cases. The synthesized NiFe{sub 2}O{sub 4} ferrite has a nanocrystalline structure with a crystallite size of about 20 and 10 nm respectively for the cases (1) and (2). The final grain size in the system (1) is about twice as large as that in the system (2), what is a consequence of different reaction paths in these two processing routes. There are five Raman and four IR active modes. Mössbauer spectroscopy studies implied on the possible cation distribution between the tetrahedral and octahedral sites in formed NiFe{sub 2}O{sub 4} spinel structure. We were able to estimate the degree of inversion at most 0.82 in the case (1) and 0.66 in the case (2).

36 MATERIALS SCIENCE↗
DOE OSTI2013

Low-temperature synthesis, structural and magnetic properties of self-dopant LaMnO{sub 3+δ} nanoparticles from a metal-organic polymeric precursor

Graphical abstract: Monophasic and highly crystalline Self-dopant LaMnO{sub 3+δ} nanoparticles (72 nm) have been successfully synthesized at low temperature (773 K) by metal citrate complex method based on Pechini-type reaction route which showed ferromagnetic interaction. Surface areas of LaMnO{sub 3+δ} nanoparticles were found to be 157.4 and 153 m{sup 2} g{sup −1} for the samples annealed at 773 K and 1173 K, respectively. - Highlights: • Self-dopant LaMnO{sub 3+δ} nanoparticles using Pechini-type reaction route at 773 K. • Size range varies from 72 to 80 nm. • Surface area varies from 153 to 157 m{sup 2} g{sup −1}. • Extensive characterization using sophisticated techniques. - Abstract: Self-dopant LaMnO{sub 3+δ} nanoparticles have been successfully synthesized by metal citrate complex method based on Pechini-type reaction route, at low temperature (773 K). Powder X-ray diffraction and transmission electron microscope revealed pure and nanostructured phase of LaMnO{sub 3+δ} (δ = 0.125) with an average grain size of ∼72 nm (773 K) and ∼80 nm (1173 K). DC-magnetization measurements under an applied magnetic field of H = ±60 kOe showed an increase in the magnetization with the increase of calcination temperature. Ferromagnetic nature shown by non-stoichiometric LaMnO{sub 3+δ} was verified by well-defined hysteresis loop with large remanent magnetization (M{sub r}) and coercive field (H{sub c}). Surface areas of LaMnO{sub 3+δ} nanoparticles were found to be 157.4 and 153 m{sup 2} g{sup −1} for the samples annealed at 773 K and 1173 K, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Structural, magnetic and catalytic properties of cobalt chromite obtained through precursor method

Highlights: • CoCr{sub 2}O{sub 4} was synthesized through the tartarate and gluconate precursor routes. • Both routes led to the formation of the single-phase CoCr{sub 2}O{sub 4}. • The crystallite size was in the range of 14–21 nm. • CoCr{sub 2}O{sub 4} samples presented ferrimagnetic ordering below Currie temperature T{sub c} = 97 K. • CoCr{sub 2}O{sub 4} samples presented catalytic performance in the total oxidation of CH{sub 4}. - Abstract: Cobalt chromite (CoCr{sub 2}O{sub 4}) was synthesized through the precursor method. The precursors: (NH{sub 4}){sub 3}[CoCr{sub 2}(C{sub 4}O{sub 6}H{sub 4}){sub 4}(OH){sub 3}]·4H{sub 2}O, (NH{sub 4}){sub 3}[CoCr{sub 2}(C{sub 6}O{sub 7}H{sub 10}){sub 4}(C{sub 6}O{sub 7}H{sub 9})]·5H{sub 2}O were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, and thermal analysis. The final oxides were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), UV–vis, IR, Raman spectroscopy (RS), magnetic measurements, N{sub 2} adsorption–desorption analyses and X-ray photoelectron spectroscopy (XPS). XRD confirmed the cubic CoCr{sub 2}O{sub 4} phase only and determined average crystallite sizes between 14 and 21 nm. Electron microscopy revealed morphology corresponding to the complete crystallization into cubic CoCr{sub 2}O{sub 4}. All the samples presented ferrimagnetic ordering below the Currie temperature (T{sub c}), and a phase transition at T{sub s} ∼26 K attributed to the onset of long-range spiral magnetic order. The CoCr{sub 2}O{sub 4} nanoparticles generated through the gluconate route following calcination at 700 °C for 1 h were found to have the best catalytic activity in the total oxidation of methane.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Nano-crystalline thin and nano-particulate thick TiO{sub 2} layer: Cost effective sequential deposition and study on dye sensitized solar cell characteristics

Highlights: • Thin TiO{sub 2} layer is deposited on conducting substrate using sol–gel based dip coating. • TiO{sub 2} nano-particles are synthesized using hydrothermal route. • Thick TiO{sub 2} particulate layer is deposited on prepared thin layer. • Dye sensitized solar cells are made using thin and thick layer based photo-anode. • Introduction of thin layer in particulate photo-anode improves the cell efficiency. - Abstract: A compact thin TiO{sub 2} passivation layer is introduced between the mesoporous TiO{sub 2} nano-particulate layer and the conducting glass substrate to prepare photo-anode for dye-sensitized solar cell (DSSC). In order to understand the effect of passivation layer, other two DSSCs are also developed separately using TiO{sub 2} nano-particulate and compact thin film based photo-anodes. Nano-particles are prepared using hydrothermal synthesis route and the compact passivation layer is prepared by simply dip coating the precursor sol prepared through wet chemical route. The TiO{sub 2} compact layer and the nano-particles are characterised in terms of their micro-structural features and phase formation behavior. It is found that introduction of a compact TiO{sub 2} layer in between the mesoporous TiO{sub 2} nano-particulate layer and the conducting substrate improves the solar to electric conversion efficiency of the fabricated cell. The dense thin passivation layer is supposed to enhance the photo-excited electron transfer and prevent the recombination of photo-excited electrons.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Hydrophobicity control by a supercritical drying technique in a sol–gel process with hybrid materials

Highlights: • Sol–gel route is combined with polymerization without using modifier. • Supercritical drying control is the key to obtain super-hydrophobic surfaces. • The whole fabrication is technologically controllable and with low costs. • The production rate is higher than 90%. • The method provides a cost-effective way for industry applications. - Abstract: We successfully synthesized one type of cheap super-hydrophobic hybrid porous materials in a sol–gel process. In this route, hydrophilic polymers and TEOS-base sol are used as precursors, the ultraviolet ray-initiated polymerization and supercritical fluid drying techniques are combined together to fulfill this task. All fabricated samples exhibit lotus-leaf-like surface structures with super-hydrophobicity. The underlying mechanisms are carefully investigated using a field-emission scanning electron microscopy (FESEM) and an X-ray photoelectron spectroscopy (XPS). We found that a well-controlled drying process is crucial to the formation of such super-hydrophobic surfaces. As high as 90% production rate is obtained in our route and thus, it might provide a cost-effective way to produce super-hydrophobic hybrid materials for industry applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Zn/ZnO dendrites arising the heat-treatment of Zn dendrites and their photocatalytic reduction of Cr(VI)

Highlights: • Zn/ZnO dendrites are prepared by an electrodeposition and subsequent annealing route. • The annealing temperature strongly affects the molar ratio of Zn/ZnO in the product. • As-prepared products can be used as the photocatalysts for the reduction of Cr(VI). • Zn/ZnO-200 presents the strongest photocatalytic activity for the reduction of Cr(VI). - Abstract: An electrodeposition-calcination route was designed for the preparation of Zn/ZnO dendrites in this work. Zn dendrites were first deposited at room temperature via a potentiostatic electrodeposition route at the potential of −1.5 V for 10 min. Then, Zn/ZnO dendrites were obtained through calcining Zn dendrites in air at 100–400 °C for 30 min. The produced Zn/ZnO dendrites were labeled as Zn/ZnO-N (N = 100, 200, 300 and 400). The investigations showed that the as-obtained Zn/ZnO-200 dendrites exhibited the strongest photocatalytic activity for the reduction of Cr (VI)–Cr (III) under the radiation of 460 mW cm{sup −2} white light from a Xenon lamp. Within 16 min, ∼92% of Cr (VI) was reduced when Zn/ZnO-200 was used as the photocatalyst. Also, the as-obtained Zn/ZnO-200 catalyst owned good stability. After six cycles, the catalytic efficiency had only slight decrease, which is favorable for reducing the cost in the practical application.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Monodisperse YVO4:Eu3+ nanospindles: Rapid converted growth and luminescence properties

Highlights: • Monodispersed YVO{sub 4} nanospindles were synthesized through conversion route. • The growth mechanism is attributed to “dissolution-recrystallization”. • Both YVO{sub 4}:Eu{sup 3+} and Au/YVO{sub 4}:Eu{sup 3+} show strong red luminescence. • The interactions between Au NPs and the YVO{sub 4}:Eu{sup 3+} NPs were discussed. - Abstract: The YVO{sub 4} nanospindles with well-crystallization were synthesized through a facile and rapid chemical conversion route. The synthesis started with the precipitation of sheet-like yttrium precursor Y{sub 2}(OH){sub 5}NO{sub 3}∙nH{sub 2}O at room temperature. With the addition of vanadate, YVO{sub 4} nanospindles were formed at the expense of the precursor in less than 10 min at 120 °C. The obtained particle shape and size are insensitive to experimental parameters, such as pH value and reaction temperature. The synthesis route is environment-friendly which involves no template or surfactant, but only relates to facile aqueous conditions at low temperature. We also investigated the luminescence properties of YVO{sub 4}:Eu{sup 3+} and gold functioned Au/YVO{sub 4}:Eu{sup 3+} products. Under UV excitation, both samples show strong red luminescence due to the radiative transitions of Eu{sup 3+}, while the excitation spectra vary significantly. The interactions between Au nanoparticles (NPs) and the YVO{sub 4}:Eu{sup 3+} NPs were also investiged.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

In-situ microwave-assisted heating synthesis of a high-performance g-C3N4/carbon nanotubes composite photocatalyst with good contact interfaces

Highlights: • One-pot microwave-assisted heating synthesis method prepared g-C{sub 3}N{sub 4} based CNTs composite photocatalyst. • Closely contact interfaces between g-C{sub 3}N{sub 4} and CNTs were prepared and observed. • WCN/CNTs exhibits a photocatalytic H{sub 2} evolution rate of 45.1 μmol/h, showing 10.02 folds of that for bulk g-C{sub 3}N{sub 4}. • WCN/CNTs exhibits a photocatalytic O{sub 2} evolution rate of 7.14 μmol/h, showing 4.61 folds of that for bulk g-C{sub 3}N{sub 4}. - Abstract: Herein, a one-pot microwave-assisted heating synthesis route was explored to prepare a g-C{sub 3}N{sub 4} based composite photocatalyst, which involved just treating of a mixture consisting of dicyandiamide and multi-walled carbon nanotubes (CNTs) using a microwave oven. The composite photocatalyst prepared by this route exhibits closely contact interfaces between g-C{sub 3}N{sub 4} and CNTs, as compared with the two ones obtained from the two-step and one-step methods previously reported, which lead to the reduced photoluminescence emission and longer lifetime of the photogenerated carriers, and the increased photocurrent response. As a result, the hydrogen evolution and oxygen evolution rates of the WCN/CNTs composite are up to 45.1 μmol/h and 7.14 μmol/h, 10.02 and 4.61 times that of BCN, respectively, which are higher than those of the other two ones prepared by the previously reported methods. This one-pot microwave-assisted heating synthesis route is suitable for preparing the g-C{sub 3}N{sub 4} based composite photocatalysts.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Sources of deactivation during glycerol conversion on Ni/γ-Al 2 O 3

Hydrogenolysis of glycerol was studied using a diluted aqueous solution of glycerol in gas phase and atmospheric pressure on Ni/γ-Al2O3 catalyst. The catalytic transformation of glycerol generates products derived from dehydration, dehydrogenation, hydrogenolysis and condensation reactions. Deep hydrogenolysis route to produce CH4 prevails in the first few hours of reaction. As the reaction time progress, dehydration-dehydrogenation products start to appear. Here, a description of the deactivation sources and its effects on the catalytic performance of Ni catalyst was proposed. The catalyst was characterized before and after the catalytic reaction by high-resolution transmission electron microscopy (HRTEM) and by employing Fourier transformed infrared spectroscopy (FTIR) of adsorbed CO. A source of deactivation was due to carbonaceous deposition. FTIR at low CO dosing pressure reveal bands assignments species essentially due to linear and bridge carbonyls, whereas high pressure CO dosing produces a complex spectra due to polycarbonyls. X-ray absorption near edge structure (XANES) analysis was employed to reveal the initial degree of reduction of the fresh catalyst. The oxidation of metallic Ni in the course of reaction may also be considered as a source of deactivation. Ni oxide species promote dehydration routes. Alumina support facilitates nickel species to be more active toward interacting with glycerol. Dehydration, which takes place on the acid sites, is the mainly route related to the generation of carbon deposition and to the observed catalyst deactivation. Another source of deactivation was due to carbiding of Ni to form Ni3C. The regeneration of used Ni catalyst was achieved by oxidation-reduction steps at 723 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Amorphous complexion-aided sintering enables scalable processing of bulk nanocrystalline Cu-Zr with high strength and compressive plasticity

Nanocrystalline alloys can have exceptional strengths, yet due to limited microstructural stability it is difficult to fabricate bulk pieces through traditional processing routes that retain nanosized grains. In this study, centimeter-sized Cu-Zr alloy pellets were fabricated via a simple and improved powder metallurgy processing route. Different consolidation temperatures and times were employed to investigate the effect of amorphous grain boundary complexions on densification and the resulting mechanical properties. Bulk compression tests were carried out, with the samples that were hot pressed at 900 °C for 10 h exhibiting an excellent combination of average yield strength of 722 ± 45 MPa and average failure strain of 25.3 ± 2.4 %. Furthermore, we find that a powder processing route which enables amorphous complexion-assisted sintering leads to samples that (1) reach full density without requiring quenching treatments or other complex processing, (2) demonstrate appreciable plasticity, and (3) have strength that competes with commercially available high-strength Cu alloys.

Bulk nanocrystalline alloy↗
DOE OSTI2013

Mo-99/Tc-99m Separation: An Assessment of Technical Options

Several strategies for the effective separation of 99mTc from 99Mo have been developed and validated. Due to the success of column chromatographic separation using acidic alumina coupled with high specific activity fission 99Mo (F 99Mo) for production of 99Mo/99mTc generators, however, most technologies until recently have generated little interest. The reduced availability of F 99Mo and consequently the shortage of 99Mo/99mTc column generators in the recent past have resurrected interest in the production of 99Mo as well as 99mTc by alternate routes. Most of these alternative production processes require separation techniques capable of providing clinical grade 99mTc from low specific activity 99Mo or irradiated Mo targets. For this reason there has been renewed interest in alternate separation routes. This paper reviews the reported separation technologies which include column chromatography, solvent extraction, sublimation and gel systems that have been traditionally used for the fabrication of 99Mo/99mTc generator systems. The comparative advantage, disadvantage, and technical challenges toward adapting the emerging requirements are discussed. New developments such as solid-phase column extraction, electrochemical separation, extraction chromatography, supported liquid membrane (SLM) and thermochromatographic techniques are also being evaluated for their potential application in the changed scenario of providing 99mTc from alternate routes. Based on the analysis provided in this review, it appears that some proven separation technologies can be quickly resurrected for the separation of clinical grade 99mTc from macroscopic levels of reactor or cyclotron irradiated molybdenum targets. Furthermore, emerging technologies can be developed further to respond to the expected changing modes of 99mTc production.

nuclear medicine↗
DOE OSTI2025

Environmental life cycle assessment methods applied to amine-ionic liquid hybrid CO 2 absorbents

A hybrid solvent mixture of triethyl(octyl)phosphonium cyanopyrrolide [P2228][2-CNPyr] and aqueous monoethanolamine (MEA) has the potential for absorbing CO 2 from post combustion flue gas. However, previous studies have found that the production of phosphonium based ionic liquids (IL) had significantly higher potential environmental impacts compared to MEA. Literature attributes these higher environmental impacts to the phosphine and phosgene-based intermediates required to produce the phosphonium ion of the ionic liquid. This study proposes a novel synthesis pathway that eliminates the need for phosphine and phosgene intermediates in the production of [P2228][2-CNPyr]. The environmental impacts of producing 1kg of the ionic liquid through this novel synthesis route was evaluated using the TRACI 2.1 methodology within the life cycle assessment (LCA) framework. Additionally, the environmental impacts for the production of 1kg of a hybrid solvent was also evaluated and compared against MEA. The life cycle inventory for the production of the IL and its hybrid solvent were calculated based on the stoichiometry and then scaled up. This study found that the IL and its hybrid solvents had higher environmental impacts among 9 of the 10 environmental impact categories calculated by the TRACI 2.1 methodology, except for the ecotoxicity potential. A sensitivity analysis indicated that these solvents were more sensitive to the assumptions of the material requirements of the phosphonium cation than the overall energy or transportation requirements. Despite this sensitivity, both the solvents demonstrated a lower Ecotoxicity Potential compared to MEA, the rest of the environmental impacts were still found to be higher than that of MEA, thereby underscoring the need to investigate novel synthesis routes for the production of phosphonium cation. The uncertainty analysis performed confirmed the findings that the IL has a higher environmental impact potentials across all categories except ecotoxicity potential. The uncertainty analysis also confirms that the phosphonium cation is a major hotspot in production route of these solvents and a source of uncertainty in the model compared to the anion. Altogether, this study underscores the need for investigating novel green chemistry pathway for the synthesis of phosphonium based ionic liquids, such as [P2228][2-CNPyr], to ensure that the these ILs can be a truly green alternative to MEA by not only offering superior CO₂ capture capacity compared to MEA but also being sustainably produced.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Poly(lactic-co-glycolic) acid loaded nano-insulin has greater potentials of combating arsenic induced hyperglycemia in mice: Some novel findings

Diabetes is a menacing problem, particularly to inhabitants of groundwater arsenic contaminated areas needing new medical approaches. This study examines if PLGA loaded nano-insulin (NIn), administered either intraperitoneally (i.p.) or through oral route, has a greater cost-effective anti-hyperglycemic potential than that of insulin in chronically arsenite-fed hyperglycemic mice. The particle size, morphology and zeta potential of nano-insulin were determined using dynamic light scattering method, scanning electronic and atomic force microscopies. The ability of the nano-insulin (NIn) to cross the blood–brain barrier (BBB) was also checked. Circular dichroic spectroscopic (CD) data of insulin and nano-insulin in presence or absence of arsenic were compared. Several diabetic markers in different groups of experimental and control mice were assessed. The mitochondrial functioning through indices like cytochrome c, pyruvate-kinase, glucokinase, ATP/ADP ratio, mitochondrial membrane potential, cell membrane potential and calcium-ion level was also evaluated. Expressions of the relevant marker proteins and mRNAs like insulin, GLUT2, GLUT4, IRS1, IRS2, UCP2, PI3, PPARγ, CYP1A1, Bcl2, caspase3 and p38 for tracking-down the signaling cascade were also analyzed. Results revealed that i.p.-injected nano-encapsulated-insulin showed better results; NIn, due to its smaller size, faster mobility, site-specific release, could cross BBB and showed positive modulation in mitochondrial signaling cascades and other downstream signaling molecules in reducing arsenic-induced-hyperglycemia. CD data indicated that nano-insulin had less distorted secondary structure as compared with that of insulin in presence of arsenic. Thus, overall analyses revealed that PLGA nano-insulin showed better efficacy in combating arsenite-induced-hyperglycemia than that of insulin and therefore, has greater potentials for use in nano-encapsulated form. - Highlights: ► PLGA encapsulated nano-insulin attenuates arsenic-induced diabetes in mice. ► Encapsulated insulin acts effectively at nearly 10 fold lesser dose than insulin. ► Injection route is more effective than oral administration route. ► Nano-insulin can cross blood–brain barrier with added physiological implications. ► Nano-insulin acts mainly through regulation of mitochondrial signaling cascade.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Part 2: Forensic attribution profiling of Russian VX in food using liquid chromatography-mass spectrometry

This work is part two of a three-part series in this issue of a Sweden-United States collaborative effort towards the understanding of the chemical attribution signatures of Russian VX (VR) in synthesized samples and complex food matrices. We describe the sourcing of VR present in food based on chemical analysis of attribution signatures by liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with multivariate data analysis. Analytical data was acquired from seven different foods spiked with VR batches that were synthesized via six different routes in two separate laboratories. The synthesis products were spiked at a lethal dose into seven food matrices: water, orange juice, apple purée, baby food, pea purée, liquid eggs and hot dog. After acetonitrile sample extraction, the samples were analyzed by LC-MS/MS operated in MRM mode. A multivariate statistical calibration model was built on the chemical attribution profiles from 118 VR spiked food samples. Using the model, an external test-set of the six synthesis routes employed for VR production was correctly identified with no observable major impact of the food matrices to the classification. The overall performance of the statistical models was found to be exceptional (94%) for the test set samples retrospectively classified to their synthesis routes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Part 3: Solid phase extraction of Russian VX and its chemical attribution signatures in food matrices and their detection by GC-MS and LC-MS [Extraction and Detection of Russian VX and its Chemical Attribution Signatures in Food and Environmental Matrices at LLNL]

Chemical attribution signatures indicative of O-isobutyl S-(2-diethylaminoethyl) methylphosphonothioate (Russian VX) synthetic routes were investigated in spiked food samples. Attribution signatures were identified using a multifaceted approach: Russian VX was synthesized using six synthetic routes and the chemical attribution signatures identified by GC-MS and LC-MS. Three synthetic routes were then down selected and spiked into complex matrices: bottled water, baby food, milk, liquid eggs, and hot dogs. Sampling and extraction methodologies were developed for these materials and used to isolate the attribution signatures and Russian VX from each matrix. Recoveries greater than 60% were achieved for most signatures in all matrices; some signatures provided recoveries greater than 100%, indicating some degradation during sample preparation. A chemometric model was then developed and validated with the concatenated data from GC-MS and LC-MS analyses of the signatures; the classification results of the model were > 75% for all samples. Finally, this work is part three of a three-part series in this issue of the United States-Sweden collaborative efforts towards the understanding of the chemical attribution signatures of Russian VX in crude materials and in food matrices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Non-unimodal and non-concave relationships in the network Macroscopic Fundamental Diagram caused by hierarchical streets

Unimodal, concave relationships between average network productivity and accumulation or density aggregated across spatially compact regions of urban networks—so called network Macroscopic Fundamental Diagrams (MFDs)—have recently been shown to exist on homogeneous street networks. When present, MFD relationships facilitate the modeling of traffic congestion at a regional level and have led to the development of various regional traffic control strategies. However, real street networks are not homogeneous—they generally have a hierarchical structure where some streets (e.g., arterials) promote higher mobility than others (e.g., local roads). Here, this paper examines how the presence of hierarchical roadway structures may potentially cause non-unimodal patterns in a network's MFD. These are observed using three types of tools: analytical models of simple network structures, simulations of various idealized roadway networks, and empirical data. The impacts of street hierarchy depend on how vehicles use different roadway types to move within the network; i.e., their routing strategy. The findings suggest that the presence of roadway hierarchies may lead to MFDs that have non-unimodal or non-concave patterns on the free-flow branch when vehicles route themselves according to user equilibrium principles, which is closest to what would be observed in realistic situations. Such patterns are contrary to what is traditionally assumed in most MFD-based modeling frameworks. However, the unimodal and concave MFD should be expected under system optimal routing conditions that maximize network productivity for a given traffic state.

42 ENGINEERING↗
DOE OSTI2021

Improving the performance of first- and last-mile mobility services through transit coordination, real-time demand prediction, advanced reservations, and trip prioritization

Socio-demographic trends and recent economic development patterns have resulted in travel behavior changes that call for more flexible and accessible public transit options. Because flexible transit services vary in scope, size, and service type, new data-informed methods are useful to optimize services based on the specific needs of local communities and riders. In this study, real-world demand and vehicle trajectory data were used to evaluate and optimize system performance for an existing first-mile–last-mile (FMLM) service in Robinson Township, PA. A general FMLM model for arbitrary demand and service supply was then developed to quantify system performance—both travel time costs and day-to-day reliability—for various operational polices considering spatio-temporal demand variation and transportation network dynamics. Heuristics were used for optimal real-time vehicle routing in sizable real-world networks accommodating various service types and scopes. In this case study, total user costs were reduced by 18.6% when rides were coordinated with mainline fixed-route transit. Predictive routing strategies were shown to marginally improve system performance under sparse and variable spatio-temporal demand. The case study also highlights potentially large travel time and user reliability improvements—reductions of 51% and 53.8%, respectively—when trip requests were made in advance of their desired pickup time. Finally, we show that travel time reliability can be improved for time-inflexible trips with trip prioritization without increasing total user costs. These results were stable to changes in demand density.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2026

Engineered plants for the production of the antioxidants arbutin and gallate

The shikimate pathway is a crucial metabolic route for the biosynthesis of numerous valuable chemicals. In this study, we engineered the shikimate pathway in plants via expression of microbial enzymes to produce the two important antioxidants gallate and arbutin. The engineered pathways utilize the aromatics protocatechuate and 4-hydroxybenzoate as metabolic intermediates. Through transient expression in Nicotiana benthamiana leaves, we first identified biosynthetic routes for the production of gallate from either chorismate or 3-dehydroshikimate. Gallate production was then achieved in Arabidopsis using a genetic background that overproduces protocatechuate and via expression of a mutated version of the 4-hydroxybenzoate hydroxylase PobA from Pseudomonas sp. Arbutin production was obtained in Arabidopsis using a genetic background that overproduces 4-hydroxybenzoate and via expression of the monooxygenase MNX1 from Candida parapsilosis. The best Arabidopsis transgenic lines accumulated gallate and arbutin in the range of 0.25 and 0.93 dry weight % (dwt%), respectively. Using sorghum for large-scale in planta production, the titers of gallate and arbutin produced from the intermediate 4-hydroxybenzoate reached 0.58 dwt% and 0.50 dwt%, respectively, in mature transgenic plants, surpassing levels typically observed in plants that naturally produce these compounds. Gallate and arbutin were readily extracted from plant tissues using methanol solvent. Analysis of extractive-free biomass showed only trace amounts of gallate and its precursors 4-hydroxybenzoate and protocatechuate crosslinked to cell walls, suggesting that they mainly occur as soluble conjugated forms stored in the vacuole. This study presents alternative synthesis routes using plant hosts for the eco-friendly production of gallate and arbutin.

Antioxidant↗