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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

The impact of core-shell nanotube structures on fracture in ceramic nanocomposites

Multi-wall carbon nanotubes (MWCNTs) can be used to create ceramic nanocomposites with improved fracture toughness. In the present work, atomic layer deposition (ALD) was employed to deposit thin oxide layers on MWCNTs. These core-shell structures were then used to create nanocomposites by using a polymer derived ceramic (PDC) to produce the matrix. Variations in both the initial MWCNT structure and the oxide layers led to substantial differences in fiber-pullout behavior. Single tube pullout tests also showed that the oxide coatings led to stronger bonding with the ceramic matrix. With high defect density MWCNTs, this led to shorter pull-out lengths which is consistent with the conventional understanding of fracture in ceramic matrix composites. However, with low defect density MWCNTs longer pullout lengths were observed with the oxide layers. To interpret the different trends that were observed, we believe that the ALD coatings should not be viewed simply as a means of altering the interfacial properties. Instead, the coated MWCNTs should be viewed as more complex core-shell fibers where both interface and internal properties can be controlled with the ALD layers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Effect of green light spectra on the reduction of retinal damage and stress in goldfish, Carassius auratus

We investigated the effect of light spectra on retinal damage and stress in goldfish using green (530 nm) and red (620 nm) light emitting diodes (LEDs) at three intensities each (0.5, 1.0, and 1.5 W/m{sup 2}). We measured the change in the levels of plasma cortisol and H{sub 2}O{sub 2} and expression and levels of caspase-3. The apoptotic response of green and red LED spectra was assessed using the terminal transferase dUTP nick end labeling (TUNEL) assay. Stress indicator (cortisol and H{sub 2}O{sub 2}) and apoptosis-related genes (caspase-3) decreased in green light, but increased in red light with higher light intensities over time. The TUNEL assay revealed that more apoptotic cells were detected in outer nuclear layers after exposure to red LED over time with the increase in light intensity, than the other spectra. These results indicate that green light efficiently reduces retinal damage and stress, whereas red light induces it. Therefore, red light-induced retina damage may induce apoptosis in goldfish retina. -- Highlights: •Green light efficiently reduces retinal damage and stress. •Green spectra reduce caspase production and apoptosis. •Red light-induced retina damage may induce apoptosis in goldfish retina. •The retina of goldfish recognizes green spectra as a stable environment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Boosting the use of bauxite residue (red mud) in cement - Production of an Fe-rich calciumsulfoaluminate-ferrite clinker and characterisation of the hydration

Highlights: • Incorporation of 35 wt% of bauxite residue for production of CSAF clinker • Thermochemical calculations as suitable tool for predicting phase assemblage • Hydration of the cement was found to be accelerated in contrast to other CSA cements. • High early compressive strengths of 40 MPa In the present work, calciumsulfoaluminate-ferrite clinker was produced using 35 wt% of bauxite residue in combination with alumina, clay, limestone and gypsum. At a temperature of 1300 °C, the hydraulic phases ye'elimite, ferrite and C{sub 2}S were formed. Computed thermochemical predictions were a significantly better match for the real mineralogy than modified Bogue equations. Hydration of the clinker led to the formation of ettringite and monosulfate, resulting in compressive strengths of 17 MPa after 28d. Compressive strengths of 40 MPa after 2d, and 28d-strengths exceeding 50 MPa, were reached in blends with 10 wt% of anhydrite. The strength development was due to the rapid formation of ettringite, mainly originating from ye'elimite, which did not convert to AFm phases and led to a compact microstructure. Only when the ye'elimite dissolution decreased, did the ferrite phase react. In pastes with additional sulfates, ferrite hydration led to the formation of ettringite and to hydrogarnet. Cement nomenclature is used in this work.{sup 1}.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Matrix-free subcell residual distribution for Bernstein finite element discretizations of linear advection equations

In this work, we introduce a new residual distribution (RD) framework for the design of bound-preserving high-resolution finite element schemes. The continuous and discontinuous Galerkin discretizations of the linear advection equation are modified to construct local extremum diminishing (LED) approximations. To that end, we perform mass lumping and redistribute the element residuals in a manner which guarantees the LED property. The hierarchical correction procedure for high-order Bernstein finite element discretizations involves localization to subcells and definition of bound-preserving weights for subcell contributions. Using strong stability preserving (SSP) Runge–Kutta methods for time integration, we prove the validity of discrete maximum principles under CFL-like time step restrictions. The low-order version of our method has roughly the same accuracy as the one derived from a piecewise (multi)-linear approximation on a submesh with the same nodal points. In high-order extensions, we use an element-based flux-corrected transport (FCT) algorithm which can be interpreted as a nonlinear RD scheme. The proposed LED corrections are tailor-made for matrix-free implementations which avoid the rapidly growing cost of matrix assembly for high-order Bernstein elements. The results for 1D, 2D, and 3D test problems compare favorably to those obtained with the best matrix-based approaches.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

A phase-field model for void and gas bubble superlattice formation in irradiated solids

A phase-field model to simulate the formation of both void and gas bubble superlattices is derived from a grand potential functional, assuming 1D diffusion of self-interstitial atoms. The model is capable of accounting for superlattice formation by either a nucleation and growth or spinodal decomposition mechanism; in this work, we focus on the nucleation and growth mechanism, using a discrete nucleation approach in the phase-field model. In simulations of void formation, short aligned rows of voids were initially formed, followed by growth in the size of the aligned rows, and finally leading to superlattice formation, consistent with experimental observations. Void superlattice spacing as a function of model parameters was quantified. Increased nucleation rates led to smaller superlattice spacing, while increased vacancy diffusivity led to larger superlattice spacing. In simulations of gas bubble superlattice formation, superlattice spacing decreased with increasing gas atom flux, consistent with experimental observations. Here, simulations with increasing ratio of gas atom flux to vacancy-interstitial pair production led to increased superlattice spacing, which is inconsistent with experimental observations at high gas atom flux rates; this discrepancy is attributed to the fact that the model does not account for bound gas atom-vacancy pairs that may dominate at high gas flux rates.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Microwave-induced selective decomposition of cellulose: Computational and experimental mechanistic study

Understanding microwave-material interactions will help facilitate the utilization of microwave technology in gasification and renewable energy production. In this study, cellulose was used as a model compound to simulate the organic matter in biomass, and its catalytic decomposition under a microwave (MW) field was studied to identify structural changes from the reaction. The study was conducted using a MW source coupled to a fixed-bed gas-flow reactor, mass spectroscopic, and Fourier transform infrared spectroscopy post-reaction analysis. Zeolite 13X was chosen as a microwave absorber to study the catalytic enhancement of the decomposition of cellulose. Density functional theory (DFT) was used to gain insights into the molecular transformations occurring in the presence of a static electric field, which was used to simulate the electric field component of the microwave electromagnetic radiation. Theoretical calculations demonstrated that both the positive and negative portion of the electric field interact with the permanent dipoles of the cellulose effecting the decomposition through the glycosidic bond breaking mechanism. The theoretical result was verified using infrared spectroscopic analysis of the pure cellulose during microwave heating. The theoretical calculations suggest only the positive electric field component may be active for the cellulose decomposition in the presence of Zeolite 13X. Physically mixing Zeolite 13X with the cellulose led to a significant enhancement in the decomposition rate of the glycosidic bond. Zeolite 13X enhanced the glycosidic O-C decomposition at lower MW power (lower temperatures), whereas the O-H functional group required higher MW power (higher temperature) for its decomposition. The DFT study coupled with the reaction studies revealed that the electric field polarizability is dependent upon both the direction and the orientation of the cellulose. Gas products revealed that applying 250 W of MW power led to the production of CO, H 2 , along with some CO 2 , CH 4 , and benzene at 305 °C. Finally, reaction under 500, 750, and 1000 W of power at constant temperature (305 °C) revealed that higher power led to the complete decomposition of cellulose to mostly CO, H 2 , and CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Structure and photoluminescence properties of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} phosphors for solid-state lighting application

Novel phosphors of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+} and Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} were synthesized by a solid-state process and characterized with X-ray diffraction, photoluminescence (PL), PL excitation (PLE), and fluorescence decay time. The relationship between the observed Ce{sup 3+} emission properties and the crystal structure of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7} is built and the result shows that Ce{sup 3+} ions occupy two non-equivalent Y{sup 3+} sites in the host. The codoping of Tb{sup 3+} in Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+} can tune the emitting colour from blue to green and increase the luminescence quantum efficiency to 75.2% by the energy transfer of Ce{sup 3+}→Tb{sup 3+}. The energy transfer processes of Ce{sup 3+}–Ce{sup 3+} and Ce{sup 3+}–Tb{sup 3+} are analysed and determined to be electric dipole–dipole and dipole–quadrupole, respectively. The broad PLE spectra of Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+} and Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} are well matched with the emission from near UV LED chips, which indicates that they are promising blue and green phosphors for phosphor-converted white LEDs. - Graphical abstract: Colour-tunable phosphors Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} with optimal quantum yield of 75.2% are synthesized and the phosphors can be served as n-UV pumped materials for LEDs. - Highlights: • Green phosphor Na{sub 2}Y{sub 2}B{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} with quantum efficiency of 75.2% for n-UV application is synthesized. • The site occupation of Ce{sup 3+} in Na{sub 2}Y{sub 2}B{sub 2}O{sub 7} is investigated with the crystal structure and photoluminescence spectra. • The energy transfer of Ce{sup 3+}–Ce{sup 3+} and Ce{sup 3+}–Tb{sup 3+}, which is responsible to the tunable emitting colour of the phosphor, is demonstrated and the mechanism is studied.

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

Effect of temperature on microstructure and mechanical properties of ECAPed (TiB + La2O3)/Ti-6Al-4V composites

Highlights: • Dynamic recrystallization resulted in ultrafine grains near TiB interface region. • Tensile strength of ECAPed composites increased by up to 18%. • The average aspect ratio of TiB reduced with increasing ECAP temperature. • Interface debonding of TiB led to crack propagation and low ductility. TiB short fibers and La{sub 2}O{sub 3} particles reinforced titanium matrix composites (TMCs) were successfully equal-channel angular pressed (ECAPed) at 600 °C–900 °C. The effect of ECAP temperature on the microstructure and mechanical properties of the TMCs was investigated. The results indicated that dislocation tangling formed cell structures in matrix at lower ECAP temperature. In contrast, continuous dynamic recrystallization occurred at higher ECAP temperature, and promoted the formation of numerous new ultrafine grains. The average aspect ratio of TiB short fibers decreased with increasing ECAP temperature, which induced interfacial debonding. The tensile strength of TMCs ECAPed at 800 °C was up to 1128 MPa, which was 18% higher than the as-received composites. Interfacial debonding led TiB short fibers in low aspect ratios disabled to bear load, while the formation of ultrafine grains increased the strength of TMCs. The coupling of these two factors resulted in little effect of ECAP temperature on the tensile strength. However, the elongation of ECAPed TMCs generally decreased due to the loss of strain hardening capacity. Stress concentration tended to occur around the tips of TiB short fibers due to the interfacial debonding and cause crack propagation. It led to the premature fracture and low ductility.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Luminescent properties and energy transfer studies of color-tunable LuBO{sub 3}: Ce{sup 3+}/Tb{sup 3+}/Eu{sup 3+} phosphors

Highlights: • A series of color-tunable LuBO{sub 3}: Ce{sup 3+}/Tb{sup 3+}/Eu{sup 3+} phosphors were synthesized. • Phosphors exhibit strong blue/green/red emission under UV excitation. • The reason of high Tb{sup 3+} content required for Ce{sup 3+} → Tb{sup 3+} → Eu{sup 3+} energy transfer is unveiled. • Green and red LED prototypes were fabricated and characterized. - Abstract: A series of LuBO{sub 3}: Ce{sup 3+}/Tb{sup 3+}/Eu{sup 3+} phosphors were synthesized via solid state reaction. The Ce{sup 3+}/Tb{sup 3+} co-doped and Ce{sup 3+}/Tb{sup 3+}/Eu{sup 3+} tri-doped phosphors absorb near UV light through 4f-5d transitions of Ce{sup 3+}, followed by sensitized Tb{sup 3+} green and Eu{sup 3+} red emission. Decay curves investigations for samples with various Tb{sup 3+} and Eu{sup 3+} contents reveal the occurrence of Ce{sup 3+} → Tb{sup 3+} → Eu{sup 3+} energy transfer. It is found that due to relative low Tb{sup 3+} → Eu{sup 3+} energy transfer rate, a high Tb{sup 3+} content (>40%) is required for efficient Ce{sup 3+} → Tb{sup 3+} → Eu{sup 3+} energy transfer. Emission color of LuBO{sub 3}: Ce{sup 3+}, Tb{sup 3+}, Eu{sup 3+} varies from blue through green to red with Ce{sup 3+}/Tb{sup 3+}/Eu{sup 3+} ratio. The quantum efficiency of LuBO{sub 3}: Ce{sup 3+}, Tb{sup 3+} green phosphor and LuBO{sub 3}: Ce{sup 3+}, Tb{sup 3+}, Eu{sup 3+} red phosphor is 50% and 30%, respectively. Green and red LED prototypes were fabricated. The results show that the obtained phosphors are potential candidates as down-converted phosphors for NUV LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structure and thermoelectric properties of bismuth telluride—Carbon composites

Highlights: • Carbon nanotubes and amorphous carbon were introduced into bismuth telluride matrix. • Carbon additives led to an increase of a phonon part of thermal conductivity. • Carbon additives led to a decrease of an electric conductivity and Seebeck coeff. - Abstract: Carbon nanotubes and amorphous carbon have been introduced into a bismuth telluride matrix (0.15 and 0.30 wt.% ratio) to investigate the influence of the carbon on the composite’s thermoelectric properties. Composites with well-dispersed additives have been obtained by sonication and ball-milling methodology. Carbon nanotubes and an amorphous carbon addition led to a decrease in electric conductivity from 1120 S/cm to 77 S/cm. The absolute value of the Seebeck coefficient was found to be reduced, changing from −113 μV/K +2 μV/K, this is attributed to electron trapping by an amorphous carbon. For all investigated composites the phonon contribution of the thermal conductivity increased in comparison with a specimen without carbon additives.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Critical role of domain crystallinity, domain purity and domain interface sharpness for reduced bimolecular recombination in polymer solar cells

In this study, inverted bulk heterojunction solar cells were fabricated using poly(3-hexylthiophene) (P3HT) blended with two different fullerene derivatives namely phenyl-C61-butyric acid methyl ester (PC 60 BM) and indene-C 60 bis-adduct (IC 60 BA). The effects of annealing temperatures on the morphology, optical and structural properties were studied and correlated to differences in photovoltaic device performance. It was observed that annealing temperature significantly improved the performance of P3HT:IC 60 BA solar cells while P3HT:PC 60 BM cells showed relatively less improvement. The performance improvement is attributed to the extent of fullerene mixing with polymer domains. Energy filtered transmission electron microscopy (EFTEM) and x-ray diffraction (XRD) results showed that ICBA mixes with disordered P3HT much more readily than PC 60 BM which leads to lower short circuit current density and fill factor for P3HT:IC 60 BA cells annealed below 120°C. Annealing above 120°C improves the crystallinity of P3HT in case of P3HT:IC 60 BA whereas in P3HT:PC 60 BM films, annealing above 80°C leads to negligible change in crystallinity. Crystallization of P3HT also leads to higher domain purity as seen EFTEM. Further it is seen that cells processed with additive nitrobenzene (NB) showed enhanced short circuit current density and power conversion efficiency regardless of the fullerene derivative used. Addition of NB led to nanoscale phase separation between purer polymer and fullerene domains. Kelvin probe force microscopy (KPFM) images showed that enhanced domain purity in additive casted films led to a sharper interface between polymer and fullerene. Lastly, enhanced domain purity and interfacial sharpness led to lower bimolecular recombination and higher mobility and charge carrier lifetime in NB modified devices.

14 SOLAR ENERGY↗
DOE OSTI2024

Dispersal of high-burnup fuel fragment surrogate particles during and after loss-of-coolant accident tests

The issue of fuel fragmentation, relocation, and dispersal is critical in the licensing and use of high-burnup (>62 GWd/MTU) nuclear fuel in light water reactors (LWRs). In this work, two test series are reported that examine the fragment dispersal during a burst event and an additional dispersal following the burst due to vibrations in the rod, such as those induced by accident recovery systems. To examine dispersal during the balloon and burst portion of a Loss-of-Coolant Accident event, HfO 2 fragments and yttria-stabilized zirconia pellets were filled into an as-fabricated cladding tube, which was then pressurized and subjected to loss-of-coolant accident testing in steam. Results from this test were found to be highly non-prototypic, and dispersal was both significantly more violent and significantly greater in magnitude than identified for actual fuel tests. These findings were attributed to the conservative (more dispersive) nature of the particles chosen for dispersal and to the details of the test conditions used that led to particularly wide bursts. Further, the second set of tests examined dispersal following the burst when vibrations were induced in the rod, primarily via recovery activities such as Emergency Core Cooling System actuation leading to rapid water addition. Post-burst dispersal testing was performed by inducing sinusoidal oscillations with 2–25 nm peak-to-peak amplitude and 2–5 Hz frequencies in pre-burst rods that had been refilled with HfO 2 fragments or high-burnup fragment surrogate mixture of HfO 2 fragments and yttria-stabilized zirconia sands. Testing revealed that rods with large burst openings (7 mm wide in this work) led to unmitigated dispersal from above the burst zone but that smaller bursts (5 mm wide), although still much larger than the mean fragment size of 3 mm, led to effectively no dispersal because of interparticle locking. Additionally, mixture and moisture were found to impact the amount of dispersal: mixtures increased dispersal, and moisture drastically reduced it. The implications of these findings on likely dispersal from actual fuel are discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Synthesis and characterization of a series of Group 4 phenoxy-thiol derivatives

In this study, a series of Group 4 phenoxy-thiols were developed from the reaction products of a series of metal tert -butoxides ([M(OBu t ) 4 ]) with four equivalents of 4-mercaptophenol (H-4MP). The products were found by single crystal X-ray diffraction to adopt the general structure [(HOBu t )(4MP) 3 M(μ-4MP)] 2 [where M = Ti (1), Zr (2), Hf (3)] from toluene and [(py) 2 M(4MP)] where M = Ti (4), Zr (5) and [(py)(4MP) 3 Hf(μ-4MP)] 2 (6) from pyridine (py). Varying the [Ti(OR) 4 ] precursors (OR = iso -propoxide (OPr i ) or neo-pentoxide (ONep)) in toluene led to [(HOR)(4MP) 3 Ti(μ-4MP)] 2 (OR = OPr i (7), ONep (8)), which were structurally similar to 1. Lower stoichiometric reactions in toluene led to partial substitution by the 4MP ligands yielding [H][Ti(μ-4MP)(4MP)(ONep) 3 ] 2 (9). Independent of the stoichiometry, all of the Ti derivatives were found to be red in color, whereas the heavier congeners were colorless. Attempts to understand this phenomenon led to investigation with a series of varied –SH substituted phenols. From the reaction of H-2MP and H-3MP (2-mercaptophenol and 3-mercaptophenol, respectively), the isolated products had identical arrangements: [(ONep) 2 (2MP)Ti(μ,η2-2MP)] 2 (10) and [(HOR)(3MP)M(μ-3MP)] 2 (M/OR = Ti/ONep (11); Zr/OBu t (12)) with a similar red color. Based on the simulated and observed UV–Vis spectra, it was reasoned that the color was generated due to a ligand-to-metal charge transfer for Ti that was not available for the larger congeners.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

2700 years of Mediterranean environmental change in central Italy: a synthesis of sedimentary and cultural records to interpret past impacts of climate on society

We report abrupt climate change in the past is thought to have disrupted societies by accelerating environmental degradation, potentially leading to cultural collapse. Linking climate change directly to societal disruption is challenging because socioeconomic factors also play a large role, with climate being secondary or sometimes inconsequential. Combining paleolimnologic, historical, and archaeological methods provides for a more secure basis for interpreting the past impacts of climate on society. We present pollen, non-pollen palynomorph, geochemical, paleomagnetic and sedimentary data from a high-resolution 2700 yr lake sediment core from central Italy and compare these data with local historical documents and archeological surveys to reconstruct a record of environmental change in relation to socioeconomic history and climatic fluctuations. Here we document cases in which environmental change is strongly linked to changes in local land management practices in the absence of clear climatic change, as well as examples when climate change appears to have been a strong catalyst that resulted in significant environmental change that impacted local communities. During the Imperial Roman period, despite a long period of stable, mild climate, and a large urban population in nearby Rome, our site shows only limited evidence for environmental degradation. Warm and mild climate during the Medieval Warm period, on the other hand, led to widespread deforestation and erosion. The ability of the Romans to utilize imported resources through an extensive trade network may have allowed for preservation of the environment near the Roman capital, whereas during medieval time, the need to rely on local resources led to environmental degradation. Cool wet climate during the Little Ice Age led to a breakdown in local land use practices, widespread land abandonment and rapid reforestation. Our results present a high-resolution regional case study that explores the effect of climate change on society for an under-documented region of Europe.

58 GEOSCIENCES↗
DOE OSTI2017

Isotopically nonstationary 13 C flux analysis of cyanobacterial isobutyraldehyde production

Here, we applied isotopically nonstationary 13 C metabolic flux analysis (INST-MFA) to compare the pathway fluxes of wild-type (WT) Synechococcus elongatus PCC 7942 to an engineered strain (SA590) that produces isobutyraldehyde (IBA). The flux maps revealed a potential bottleneck at the pyruvate kinase (PK) reaction step that was associated with diversion of flux into a three-step PK bypass pathway involving the enzymes PEP carboxylase (PEPC), malate dehydrogenase (MDH), and malic enzyme (ME). Overexpression of pk in SA590 led to a significant improvement in IBA specific productivity. Single-gene overexpression of the three enzymes in the proposed PK bypass pathway also led to improvements in IBA production, although to a lesser extent than pk overexpression. Combinatorial overexpression of two of the three genes in the proposed PK bypass pathway ( mdh and me ) led to improvements in specific productivity that were similar to those achieved by single-gene pk overexpression. Our work demonstrates how 13 C flux analysis can be used to identify potential metabolic bottlenecks and novel metabolic routes, and how these findings can guide rational metabolic engineering of cyanobacteria for increased production of desired molecules.

13C INST-MFA↗
DOE OSTI2019

Grassroots Efforts To Quantify and Improve the Academic Climate of an R1 STEM Department: Using Evidence-Based Discussions To Foster Community

Women and some racial and ethnic groups remain underrepresented in chemistry departments across the United States, and generally, efforts to improve representation have resulted in minimal or no improvements in the last 10 years. Here, we present the outcomes of a graduate-student-led initiative that sought to assess the issues affecting inclusivity, diversity, and wellness within the Department of Chemistry at the University of California, Berkeley. We report how the results of a department-tailored academic climate survey were used to develop a method to foster open, productive discussion among graduate students, postdoctoral researchers, and faculty. This event format led to an improved understanding of the challenges facing our community members, as well as the identification of strategies that can be used to make the Department of Chemistry more welcoming for all members. We report the success of this student-led effort to highlight the value of assessing diversity and inclusion at the department-level, as well as the benefits of using community data to stimulate productive, evidence-based discussions. Furthermore, we envision that these methods can be implemented within any research-focused academic community to promote positive cultural change.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Discovery and Characterization of 2-Acylaminoimidazole Microsomal Prostaglandin E Synthase-1 Inhibitors

As part of a program aimed at the discovery of antinociceptive therapy for inflammatory conditions, a screening hit was found to inhibit microsomal prostaglandin E synthase-1 (mPGES-1) with an IC 50 of 17.4 μM. Structural information was used to improve enzyme potency by over 1000-fold. Addition of an appropriate substituent alleviated time-dependent cytochrome P450 3A4 (CYP3A4) inhibition. Further structure–activity relationship (SAR) studies led to 8, which had desirable potency (IC 50 = 12 nM in an ex vivo human whole blood (HWB) assay) and absorption, distribution, metabolism, and excretion (ADME) properties. Here, studies on the formulation of 8 identified 8·H 3 PO 4 as suitable for clinical development. Omission of a lipophilic portion of the compound led to 26, a readily orally bioavailable inhibitor with potency in HWB comparable to celecoxib. Furthermore, 26 was selective for mPGES-1 inhibition versus other mechanisms in the prostanoid pathway. These factors led to the selection of 26 as a second clinical candidate.

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

Droop-Free Colloidal Quantum Dot Light-Emitting Diodes

Colloidal semiconductor quantum dots (QDs) are a highly promising materials platform for implementing solution-processable light-emitting diodes (LEDs). They combine high photostability of traditional inorganic semiconductors with chemical flexibility of molecular systems, which makes them well-suited for large-area applications such as television screens, solid-state lighting, and outdoor signage. Additional beneficial features include size-controlled emission wavelengths, narrow bandwidths, and nearly perfect emission efficiencies. State-of-the-art QD-LEDs exhibit high internal quantum efficiencies approaching unity. However, these peak values are observed only at low current densities (J) and correspondingly low brightnesses, whereas at higher J, the efficiency usually exhibits a quick roll-off. This efficiency droop limits achievable brightness levels and decreases device longevity due to excessive heat generation. We demonstrate QD-LEDs operating with high internal efficiencies (up to 70%) virtually droop-free up to unprecedented brightness of >100,000 cd m –2 (at ~500 mA cm –2 ). This exceptional performance is derived from specially engineered QDs that feature a compositionally graded interlayer and a final barrier layer. This QD design allows for improved balance between electron and hole injections combined with considerably suppressed Auger recombination, which helps mitigate efficiency losses due to charge imbalance at high currents. Finally, these results indicate a significant potential of newly developed QDs as enablers of future ultrabright, highly efficient devices for both indoor and outdoor applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗