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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Persistent fibrosis in the liver of choline-deficient and iron-supplemented L-amino acid-defined diet-induced nonalcoholic steatohepatitis rat due to continuing oxidative stress after choline supplementation

Nonalcoholic steatohepatitis (NASH) is characterized by combined pathology of steatosis, lobular inflammation, fibrosis, and hepatocellular degeneration, with systemic symptoms of diabetes or hyperlipidemia, all in the absence of alcohol abuse. Given the therapeutic importance and conflicting findings regarding the potential for healing the histopathologic features of NASH in humans, particularly fibrosis, we investigated the reversibility of NASH-related findings in Wistar rats fed a choline-deficient and iron-supplemented L-amino acid-defined (CDAA) diet for 12 weeks, with a recovery period of 7 weeks, during which the diets were switched to a choline-sufficient and iron-supplemented L-amino acid-defined (CSAA) one. Analysis showed that steatosis and inflammation were significantly resolved by the end of the recovery period, along with decreases in AST and ALT activities within 4 weeks. In contrast, fibrosis remained even after the recovery period, to an extent similar to that in continuously CDAA-fed animals. Real-time reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemical investigations revealed that expression of some factors indicating oxidative stress (CYP2E1, 4-HNE, and iNOS) were elevated, whereas catalase and SOD1 were decreased, and a hypoxic state and CD34-positive neovascularization were evident even after the recovery period, although the fibrogenesis pathway by activated α-SMA-positive hepatic stellate cells via TGF-β and TIMPs decreased to the CSAA group level. In conclusion, persistent fibrosis was noted after the recovery period of 7 weeks, possibly due to sustained hypoxia and oxidative stress supposedly caused by capillarization. Otherwise, histopathological features of steatosis and inflammation, as well as serum AST and ALT activities, were recovered. - Highlights: ► NASH-like liver lesions are induced in rats by feeding a CDAA diet. ► Steatosis and lobular inflammation are resolved after switching to a CSAA diet. ► Fibrosis is sustained, possibly due to continuing hypoxia and oxidative stress.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Liver biomarker and in vitro assessment confirm the hepatic origin of aminotransferase elevations lacking histopathological correlate in beagle dogs treated with GABA{sub A} receptor antagonist NP260

NP260 was designed as a first-in-class selective antagonist of α4-subtype GABA{sub A} receptors that had promising efficacy in animal models of pain, epilepsy, psychosis, and anxiety. However, development of NP260 was complicated following a 28-day safety study in dogs in which pronounced elevations of serum aminotransferase levels were observed, although there was no accompanying histopathological indication of hepatocellular injury. To further investigate the liver effects of NP260, we assayed stored serum samples from the 28-day dog study for liver specific miRNA (miR-122) as well as enzymatic biomarkers glutamate dehydrogenase and sorbitol dehydrogenase, which indicate liver necrosis. Cytotoxicity assessments were conducted in hepatocytes derived from dog, rat, and human liver samples to address the species specificity of the liver response to NP260. All biomarkers, except ALT, returned toward baseline by Day 29 despite continued drug treatment, suggesting adaptation to the initial injury. In vitro analysis of the toxicity potential of NP260 to primary hepatocytes indicated a relative sensitivity of dog > human > rat, which may explain, in part, why the liver effects were not evident in the rodent safety studies. Taken together, the data indicate that a diagnostic biomarker approach, coupled with sensitive in vitro screening strategies, may facilitate interpretation of toxicity potential when an adaptive event masks the underlying toxicity. - Highlights: • NP260 caused ALT elevations in dogs without evidence of hepatocellular injury. • SDH, GLDH, and miRNA-122 elevations occurred, confirming hepatocellular necrosis. • NP260 toxicity is greater in dog and human hepatocytes than in rat hepatocytes. • Species sensitivity may explain why the rodent studies failed to indicate risk. • Diagnostic biomarkers and hepatocyte studies aid interpretation of hepatotoxicity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Dysregulation of protein degradation pathways may mediate the liver injury and phospholipidosis associated with a cationic amphiphilic antibiotic drug

A large number of antibiotics are known to cause drug-induced liver injury in the clinic; however, interpreting clinical risk is not straightforward owing to a lack of predictivity of the toxicity by standard preclinical species and a poor understanding of the mechanisms of toxicity. An example is PF-04287881, a novel ketolide antibiotic that caused elevations in liver function tests in Phase I clinical studies. In this study, a mouse diversity panel (MDP), comprised of 34 genetically diverse, inbred mouse strains, was utilized to model the toxicity observed with PF-04287881 treatment and investigate potential mechanisms that may mediate the liver response. Significant elevations in serum alanine aminotransferase (ALT) levels in PF-04287881-treated animals relative to vehicle-treated controls were observed in the majority (88%) of strains tested following a seven day exposure. The average fold elevation in ALT varied by genetic background and correlated with microscopic findings of hepatocellular hypertrophy, hepatocellular single cell necrosis, and Kupffer cell vacuolation (confirmed as phospholipidosis) in the liver. Global liver mRNA expression was evaluated in a subset of four strains to identify transcript and pathway differences that distinguish susceptible mice from resistant mice in the context of PF-04287881 treatment. The protein ubiquitination pathway was highly enriched among genes associated with PF-04287881-induced hepatocellular necrosis. Expression changes associated with PF-04287881-induced phospholipidosis included genes involved in drug transport, phospholipid metabolism, and lysosomal function. The findings suggest that perturbations in genes involved in protein degradation leading to accumulation of oxidized proteins may mediate the liver injury induced by this drug. - Highlights: • Identified susceptible and resistant mouse strains to liver injury induced by a CAD • Liver injury characterized by single cell necrosis, and phospholipidosis • Decreased gene expression associated with protein ubiquitination in sensitive mice • Altered protein ubiquitination may cause oxidized protein accumulation in the liver.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Tetrachloro-p-benzoquinone induces hepatic oxidative damage and inflammatory response, but not apoptosis in mouse: The prevention of curcumin

This study investigated the protective effects of curcumin on tetrachloro-p-benzoquinone (TCBQ)-induced hepatotoxicity in mice. TCBQ-treatment causes significant liver injury (the elevation of serum AST and ALT activities, histopathological changes in liver section including centrilobular necrosis and inflammatory cells), oxidative stress (the elevation of TBAR level and the inhibition of SOD and catalase activities) and inflammation (up-regulation of iNOS, COX-2, IL-1β, IL-6, TNF-α and NF-κB). However, these changes were alleviated upon pretreatment with curcumin. Interestingly, TCBQ has no effect on caspase family genes or B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X (Bax) protein expressions, which implied that TCBQ-induced hepatotoxicity is independent of apoptosis. Moreover, curcumin was shown to induce phase II detoxifying/antioxidant enzymes HO-1 and NQO1 through the activation of nuclear factor erythroid-derived 2-like 2 (Nrf2). In summary, the protective mechanisms of curcumin against TCBQ-induced hepatoxicity may be related to the attenuation of oxidative stress, along with the inhibition of inflammatory response via the activation of Nrf2 signaling. - Highlights: • TCBQ-intoxication significantly increased AST and ALT activities. • TCBQ-intoxication induced oxidative stress in mice liver. • TCBQ-intoxication induced inflammatory response in mice liver. • TCBQ-intoxication induced hepatotoxicity is independent of apoptosis. • Curcumin relieved TCBQ-induced liver damage remarkably.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

S-adenosyl-L-methionine protection of acetaminophen mediated oxidative stress and identification of hepatic 4-hydroxynonenal protein adducts by mass spectrometry

Acetaminophen (APAP) hepatotoxicity is protected by S-adenosyl-L-methionine (SAMe) treatment 1 hour (h) after APAP in C57/Bl6 mice. This study examined protein carbonylation as well as mitochondrial and cytosolic protein adduction by 4-hydroxynonenal (4-HNE) using mass spectrometry (MS) analysis. Additional studies investigated the leakage of mitochondrial proteins and 4-HNE adduction of these proteins. Male C57/Bl6 mice (n = 5/group) were divided into the following groups and treated as indicated: Veh (15 ml/kg water, ip), SAMe (1.25 mmol/kg, ip), APAP (250 mg/kg), and SAMe given 1 h after APAP (S + A). APAP toxicity was confirmed by an increase (p < 0.05) in plasma ALT (U/l) and liver weight/10 g body weight relative to the Veh, SAMe and S + A groups 4 h following APAP treatment. SAMe administered 1 h post-APAP partially corrected APAP hepatotoxicity as ALT and liver weight/10 g body weights were lower in the S + A group compared the APAP group. APAP induced leakage of the mitochondrial protein, carbamoyl phosphate synthase-1 (CPS-1) into the cytosol and which was reduced in the S + A group. SAMe further reduced the extent of APAP mediated 4-HNE adduction of CPS-1. MS analysis of hepatic and mitochondrial subcellular fractions identified proteins from APAP treated mice. Site specific 4-HNE adducts were identified on mitochondrial proteins sarcosine dehydrogenase and carbamoyl phosphate synthase-1 (CPS-1). In summary, APAP is associated with 4-HNE adduction of proteins as identified by MS analysis and that CPS-1 leakage was greater in APAP treated mice. SAMe reduced the extent of 4-HNE adduction of proteins as well as leakage of CPS-1. - Highlights: • Acetaminophen (APAP) toxicity protected by S-adenosylmethionine (SAMe) • 4-Hydroxynonenal adducted to sarcosine dehydrogenase • 4-Hydroxynonenal adducted to carbamoyl phosphate synthetase-1 • SAMe reduced APAP mediated CPS-1 mitochondrial leakage.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

MicroRNA-mediated Th2 bias in methimazole-induced acute liver injury in mice

MicroRNA (miRNA) is a class of small non-coding RNAs containing approximately 20 nucleotides that negatively regulate target gene expression. Little is known about the role of individual miRNAs and their targets in immune- and inflammation-related responses in drug-induced liver injury. In the present study, involvement of miRNAs in the T helper (Th) 2-type immune response was investigated using a methimazole (MTZ)-induced liver injury mouse model. Co-administration of L-buthionine-S,R-sulfoximine and MTZ induced acute hepatocellular necrosis and elevated plasma levels of alanine aminotransferase (ALT) from 4 h onward in female Balb/c mice. The hepatic mRNA expression of Th2 promotive factors was significantly increased concomitantly with plasma ALT levels. In contrast, the hepatic mRNA expression of Th2 suppressive factors was significantly decreased during the early phase of liver injury. Comprehensive profiling of hepatic miRNA expression was analyzed before the onset of MTZ-induced liver injury. Using in silico prediction of miRNAs that possibly regulate Th2-related genes and subsequent quantification, we identified up-regulation of expression of miR-29b-1-5p and miR-449a-5p. Among targets of these miRNAs, down-regulation of Th2 suppressive transcription factors, such as SRY-related HMG-box 4 (SOX4) and lymphoid enhancer factor-1 (LEF1), were observed from the early phase of liver injury. In conclusion, negative regulation of the expression of SOX4 by miR-29b-1-5p and that of LEF1 by miR-449a-5p is suggested to play an important role in the development of Th2 bias in MTZ-induced liver injury. - Highlights: • Methimazole induced hepatic Th2 bias in the pathogenesis of liver injury in mice. • Rapid down-regulation of SOX4 and LEF1 may initiate and/or maintain hepatic Th2 bias. • Negative regulation of SOX4 by miR-29b-1-5p and LEF1 by miR-449a-5p was suggested.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Small Molecule Acceptor and Polymer Donor Crystallinity and Aggregation Effects on Microstructure Templating: Understanding Photovoltaic Response in Fullerene-Free Solar Cells

Perylenediimide (PDI) small molecule acceptor (SMA) crystallinity and donor polymer aggregation and crystallinity effects on bulk-heterojunction microstructure and polymer solar cell (PSC) performance are systematically investigated. Two highperformance polymers, semicrystalline poly[5-(2-hexyldodecyl)-4Hthieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-yl-alt-4,4''dodecyl-2,2':5',2''- terthiophene-5,5''-diyl] (PTPD3T or D1) and amorphous poly{4,8- bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene- 2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-2-carboxylate-2,6-diyl) (PBDTT-FTTE or D2), are paired with three PDI-based SMAs (A1-A3) of differing crystallinity (A1 is the most, A3 is the least crystalline). The resulting PSC performance trends are strikingly different from those of typical fullerene-based PSCs and are highly material-dependent. The present trends reflect synergistic aggregation propensities between the SMA and polymer components. Importantly, the active layer morphology is templated by the PDI in some blends and by the polymer in others, with the latter largely governed by the polymer aggregation. Thus, PTPD3T templating capacity increases as self-aggregation increases (greater Mn), optimizing PSC performance with A2, while A3-based cells exhibit an inverse relationship between polymer aggregation and performance, which is dramatically different from fullerene-based PSCs. For PBDTT-FTTE, A2-based cells again deliver the highest PCEs of ~5%, but here both A2 and PBDTT-FTTE (medium Mn) template the morphology. Overall, the present results underscore the importance of nonfullerene acceptor aggregation for optimizing PSC performance and offer guidelines for pairing SMAs with acceptable donor polymers.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structure and Conductivity of Semiconducting Polymer Hydrogels

Poly(fluorene-alt-thiophene) (PFT) is a conjugated polyelectrolyte that self-assembles into rod-like micelles in water, with the conjugated polymer backbone running along the length of the micelle. At modest concentrations (-10 mg/mL in aqueous solutions), PFT forms hydrogels, and this work focuses on understanding the structure and intermolecular interactions in those gel networks. The network structure can be directly visualized using cryo electron microscopy. Oscillatory rheology studies further tell us about connectivity within the gel network, and the data are consistent with a picture where polymer chains bridge between micelles to hold the network together. Addition of tetrahydrofuran (THF) to the gels breaks those connections, but once the THF is removed, the gel becomes stronger than it was before, presumably due to the creation of a more interconnected nanoscale architecture. Small polymer oligomers can also passivate the bridging polymer chains, breaking connections between micelles and dramatically weakening the hydrogel network. Fits to solution-phase small-angle X-ray scattering data using a Dammin bead model support the hypothesis of a bridging connection between PFT micelles, even in dilute aqueous solutions. Finally, time-resolved microwave conductivity measurements on dried samples show an increase in carrier mobility after THF annealing of the PFT gel, likely due to increased connectivity within the polymer network.

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

Electrolyte Immersion Increases Photoconductivity in a Model Polymer Photocathode

Immersing polymer solar cells in aqueous electrolyte for photoelectrochemical (PEC) hydrogen production is likely to cause photophysical changes that could present both challenges and opportunities for engineering functional and durable devices. Herein we study the bulk heterojunction blend poly(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)-alt-(2-(((2-ethylhexyl)oxy)carbonyl)-3-fluorothieno[3,4-b]thiophene-4,6-diyl):poly(N,N'-di(2-octyldodecyl)naphthalene-1,8:4,5-bis(dicarboximide)-2,6-diyl)-alt-(2,2-bithiophene-5,5'-diyl) (PTB7-Th:N2200) excited-state dynamics in electrolyte from femtosecond to millisecond time scales using pump-probe microwave conductivity and absorption spectroscopy. While the blend swells very little, electrolyte exposure increases the microwave-frequency mobility and possibly the yield of photogenerated charges while also decreasing crystallinity. These results indicate an enhancement in key performance metrics, implying that any limitations on the performance of PEC test devices do not arise from active layer-electrolyte interactions. For the PTB7-Th:N2200 blend or similar photocathode systems, our results indicate that improving the interfacial kinetics and/or the carrier lifetime should be prioritized, not protecting the active layer from the electrolyte. Since this observation may not be universal to all polymer systems, future research should focus on identifying their limiting photophysical processes. electrolyte.

14 SOLAR ENERGY↗
DOE OSTI2021

High-Field One-Dimensional and Two-Dimensional 27Al Magic-Angle Spinning Nuclear Magnetic Resonance Study of ?-, d-, and ?-Al2O3 Dominated Aluminum Oxides: Toward Understanding the Al Sites in ?-Al2O3

Herein, a detailed analysis was carried out using high-field (19.9 T) 27Al magic-angle spinning (MAS) nuclear magnetic resonance (NMR) on three specially prepared aluminum oxide samples where the ?-, d-, and ?-Al2O3 phases are dominantly expressed through careful control of the synthesis conditions. Specifically, two-dimensional (2D) multiquantum (MQ) MAS 27Al was used to obtain high spectral resolution, which provided a guide for analyzing quantitative 1D 27Al NMR spectra. Six aluminum sites were resolved in the 2D MQ MAS NMR spectra, and seven aluminum sites were required to fit the 1D spectra. A set of octahedral and tetrahedral peaks with well-defined quadrupolar line shapes was observed in the ?-phase dominant sample and was unambiguously assigned to the ?-Al2O3 phase. The distinct line shapes related to the ?-Al2O3 phase provided an opportunity for effectively deconvoluting the more complex spectrum obtained from the d-Al2O3 dominant sample, allowing the peaks/quadrupolar parameters related to the d-Al2O3 phase to be extracted. The results show that the d-Al2O3 phase contains three distinct AlO sites and three distinct AlT sites. This detailed Al site structural information offers a powerful way of analyzing the most complex ?-Al2O3 spectrum. It is found that the ?-Al2O3 phase consists of Al sites with local structures similar to those found in the d-Al2O3 and ?-Al2O3 phases albeit with less ordering. Spin–lattice relaxation time measurement further confirms the disordering of the lattice. Collectively, this study uniquely assigns 27Al features in transition aluminas, offering a simplified method to quantify complex mixtures of aluminum sites in transition alumina samples.

Xu, Suochang↗
DOE OSTI2012

Structure and Mechanical Behavior of Elastomeric Multiblock Terpolymers Containing Glassy, Rubbery, and Semicrystalline Blocks

Multiblock copolymers containing glassy poly(cyclohexylethylene) (C), rubbery poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were synthesized by sequential anionic polymerization of styrene, isoprene, and butadiene followed by catalytic hydrogenation. The resulting CECPCEC (denoted XPX) and CECP (XP) multiblock copolymers each contain 50 vol % of P and equal amounts of C and E. These materials have been studied by dynamic mechanical spectroscopy (DMS), transmission electron microscopy (TEM), small- and wide-angle X-ray scattering (SAXS and WAXS), differential scanning calorimetry (DSC), and tensile deformation to characterize the morphology, phase behavior, and mechanical properties. Microphase separation in these compounds is induced by crystallization of E and/or chemical incompatibility between the three blocks, leading to a new type of morphology which contains continuous region of P and continuous region of microphase-separated X, resulting in mechanically resilient materials. High molecular weight block copolymers microphase separate with two different length scales associated with segregation between C and E and X and P. These structural features produce a nonclassical scaling relationship for the C-E domain spacing, d {approx} N{sup 0.31}, where N is the degree of polymerization of CEC portion. The role of semicrystalline E domains during uniaxial deformation has been exposed with WAXS experiments, which support a two-step mechanism involving recoverable and nonrecoverable deformation to different extents. Strain hardening is observed in double-anchored XPX, but not in single-anchored XP, at large tensile strains.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Effect of chiral 2-ethylhexyl side chains on chiroptical properties of the narrow bandgap conjugated polymers PCPDTBT and PCDTPT

Two narrow bandgap conjugated polymers containing chiral 2-ethylhexyl side chains were synthesized: poly[(4,4-bis(2-ethylhexyl)cyclopenta-[2,1-b:3,4-b']dithiophene)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl] (PCPDTBT*) and poly[(4,4-bis(2-ethylhexyl)cyclopenta[2,1-b:3,4-b0]dithiophene)-2,6-diyl-alt-[1,2,5]-thiadiazolo[3,4-c]pyridine] (PCDTPT*). The presence of a chiral substituent provides a handle to study the geometry of interchain aggregates and/or the secondary structure of these conjugated polymers in solution and in thin films via circular dichroism (CD) spectroscopy, provided that the asymmetry in the side-chain is translated to the optically active conjugated backbone. CD signals are observed for PCPDTBT* and PCDTPT* in poor solvent systems, which indicate the presence of chiral ordering in the aggregates. PCPDTBT* shows greater chiral order than PCDTPT* based on their relative anisotropy factors. Additionally, GIWAXS analysis reveals that PCPDTBT* films are more ordered than what is observed for the same polymer containing racemic 2-ethylhexyl chains. Upon solution deposition, the chiral ordering is found to translate to the solid-state microstructure for PCPDTBT* but not PCDTPT*. The presence of a pyridyl nitrogen on the thiadiazolo[3,4-c]pyridine ring of PCDTPT* favors a planar conformation for the backbone such that it has a higher rotational barrier compared to PCPDTBT*. This larger rotational barrier appears to limit the ability of PCDTPT* to adopt a helical structure or relevant chain distortions for achieving chiral aggregates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

New donor polymer with tetrafluorinated blocks for enhanced performance in perylenediimide-based solar cells

The synthesis of a new tetrafluorinated semiconducting donor polymer, poly[(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene)-alt-(5,6-difluoro-4,7-(4-(2-ethylhexyl)-dithien-2-yl-2,1,3-benzothiadiazole)] (PBTZF4), and its photovoltaic performance in bulk heterojunction (BHJ) blends with the non-fullerene molecular acceptor [1,2:3,4]-bis-[N,N'-bis-1-pentylhexyl-perylenediimide-1,12-yl]-benzene (bPDI2P), are reported. PBTZF4:bPDI2P solar cells exhibit a high open circuit voltage (V oc ) of 1.118 V, a short circuit current density (J sc ) of 10.02 mA cm –2 , and a fill factor (FF) of 49.5%, affording a power conversion efficiency (PCE) of 5.55%. Interestingly, a lower PCE of 3.68% is obtained with the difluorinated analogue, poly[(4,8-bis(5-(2-ethylhexyl)-thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene)- alt -(5,6-difluoro-4,7-(4-(2-ethyl-hexyl)-dithien-2-yl-2,1,3-benzothiadiazole)] (PBTZF2). Both PBTZF4:bPDI2P and PBTZF2:bPDI2P cells benefit from complementary (donor/acceptor) light absorption and very low geminate recombination, with bimolecular recombination being the dominant loss mechanism, as established by femtosecond transient absorption spectroscopy. DFT computation and physicochemical characterization data argue that the “additional” tetrafluorination planarizes the PBTZF4 backbone and enhances aggregation versus PBTZF2, affording superior charge carrier transport as assayed by field-effect mobility. In addition, fluorine-originated HOMO stabilization, –5.41 eV for PBTZF4 versus –5.33 eV for PBTZF2, and a superior blend microstructure afford a higher PBTZF4:bPDI2P solar cell PCE versus PBTZF2:bPDI2P.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Accelerating ion transport by dynamic asymmetry of alternating polymer electrolytes

Polymer based electrolytes allow the absence of volatile components in batteries thus increasing their safety. Yet, they exhibit drawbacks based on their low conductivity. We have used an alternating polymer consisting of dimethyl siloxane (DMS) and ethylene glycol (EG) blocks to circumvent known disadvantages of the usually used polyethylene glycol (PEG). Incorporating dimethyl siloxane lowers the glass-transition temperature and thus reduces the segmental relaxation time, by dynamic asymmetry or internal plasticization of the constituting polymer blocks. The alternating structure ensures miscibility of the different components and hinders crystallization. Furthermore, the pure polymer, P(DMS 3 -alt-EG 4 ), shows a segmental relaxation time well in the range needed for polymer electrolytes. Mixtures of LiClO 4 and P(DMS 3 -alt-EG 4 ) show a drastically reduced temperature dependence of their DC conductivity in comparison to PEG based systems, resulting in an increase by two orders of magnitude at T = 5 °C and even three to four orders of magnitude at T = 0 °C. Addition of coordinating (acetonitrile) or non-coordinating (toluene) solvent increases conductivity either via additional plasticization or by weakening the Li-binding yet looking at the dynamics at low concentrations of additional solvent the mobility of the polymer is reduced. In conclusion, the solvent addition leads only at higher solvent concentration to a reduction in relaxation time.

Jakobi, Bruno [Louisiana State Univ., Baton Rouge,↗
DOE OSTI2015

Combined heat and power generation with a HCPV system at 2000 suns

This work shows the development of an innovative solar CHP system for the combined production of heat and power based upon HCPV modules working at the high concentration level of 2000 suns. The solar radiation is concentrated on commercial InGaP/InGaAs/Ge triple-junction solar cells designed for intensive work. The primary optics is a rectangular off-axis parabolic mirror while a secondary optic at the focus of the parabolic mirror is glued in optical contact with the cell. Each module consist of 2 axis tracker (Alt-Alt type) with 20 multijunction cells each one integrated with an active heat sink. The cell is connected to an active heat transfer system that allows to keep the cell at a high level of electrical efficiency (ηel > 30 %), bringing the heat transfer fluid (water and glycol) up to an output temperature of 90°C. Accordingly with the experimental data collected from the first 1 kWe prototype, the total amount of extracted thermal energy is above the 50% of the harvested solar radiation. That, in addition the electrical efficiency of the system contributes to reach an overall CHP efficiency of more than the 80%.

14 SOLAR ENERGY↗
DOE OSTI2023

Drying of tundra landscapes will limit subsidence-induced acceleration of permafrost thaw

We used a model for permafrost hydrology informed by detailed measurements of soil ice content to better understand the potential risk of abrupt permafrost thaw triggered by melting ground ice, a key open question associated with permafrost response to a warming Arctic. Our spatially resolved simulations of a well-characterized site in polygonal tundra near Utqiaġvik, Alaska, agree well with multiple types of observations in the current climate. Projections indicate 63 cm of bulk subsidence from 2006 to 2100 in the strong-warming Representative Concentration Pathway 8.5 climate. Permafrost thaw as measured by the increase in active layer thickness (ALT)—the thickness of the soil layer that thaws each summer—is accelerated by subsidence, but the effect is relatively small. The ALT increases from the current-day value of approximately 50 cm to approximately 180 cm by 2100 when subsidence is included compared to about 160 cm when it is neglected. In these simulations, previously identified positive feedbacks between subsidence and thaw are self-limiting on decadal time frames because landscape runoff and increasing evapotranspiration result in drier tundra with weaker surface/atmosphere coupling. These results for a tundra site that is representative of large swathes of the Alaska North Slope suggest that subsidence is unlikely to lead to abrupt thaw over large areas. However, subsidence does have significant effects on the hydrology of polygonal tundra. Specifically, subsidence increases landscape runoff, which helps maintain streamflow in the face of increased evapotranspiration but also causes drier tundra conditions that could have deleterious effects on sensitive Arctic wetland ecosystems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Electrolytes with moderate lithium polysulfide solubility for high-performance long-calendar-life lithium–sulfur batteries

Lithium–sulfur (Li-S) batteries with high energy density and low cost are promising for next-generation energy storage. However, their cycling stability is plagued by the high solubility of lithium polysulfide (LiPS) intermediates, causing fast capacity decay and severe self-discharge. Exploring electrolytes with low LiPS solubility has shown promising results toward addressing these challenges. However, here, we report that electrolytes with moderate LiPS solubility are more effective for simultaneously limiting the shuttling effect and achieving good Li-S reaction kinetics. We explored a range of solubility from 37 to 1,100 mM (based on S atom, [S]) and found that a moderate solubility from 50 to 200 mM [S] performed the best. Using a series of electrolyte solvents with various degrees of fluorination, we formulated the S ingle- S olvent, S ingle- S alt, S tandard S alt concentration with M oderate L i PSs so l ubility E lectrolytes (termed S 6 MILE ) for Li-S batteries. Among the designed electrolytes, Li-S cells using fluorinated-1,2-diethoxyethane S 6 MILE (F4DEE-S 6 MILE) showed the highest capacity of 1,160 mAh g −1 at 0.05 C at room temperature. At 60 °C, fluorinated-1,4-dimethoxybutane S 6 MILE (F4DMB-S 6 MILE) gave the highest capacity of 1,526 mAh g −1 at 0.05 C and an average CE of 99.89% for 150 cycles at 0.2 C under lean electrolyte conditions. This is a fivefold increase in cycle life compared with other conventional ether-based electrolytes. Moreover, we observed a long calendar aging life, with a capacity increase/recovery of 4.3% after resting for 30 d using F4DMB-S 6 MILE. Furthermore, the correlation between LiPS solubility, degree of fluorination of the electrolyte solvent, and battery performance was systematically investigated.

25 ENERGY STORAGE↗
DOE OSTI2014

The impacts of permafrost thaw on land-atmosphere greenhouse gas exchange

Permafrost thaw and the subsequent mobilization of carbon stored in previously frozen soil organic matter (SOM) would be a strong positive feedback to climate1. As the northern permafrost region experiences double the rate of warming as the rest of the Earth2, the vast amount of carbon in permafrost soils3 is vulnerable to thaw, decomposition and release as atmospheric greenhouse gases (GHG). Here, we employ a process-based model simulation experiment to assess the net effect of this so-called permafrost carbon feedback (PCF) in recent decades. Results show a wide-spread increase in the depth to permafrost between 1990 and 2006, with simulated active layer thickness (ALT) capturing the mean and spatial variability of the observational data. Analysis of the simulation experiment provides an estimate of a 2.8 mm/yr increase in permafrost depth, which translates to 281 TgC/yr thawed from previously frozen SOM. Overall, we estimate a net GHG forcing of 534 MtCO2eq/yr directly tied to ALT dynamics, while accounting for CO2 (562 MtCO2eq/yr) and CH4 (52 MtCO2eq/yr) release as well as CO2 uptake by vegetation (-80 MtCO2eq/yr). This net forcing represents a significant factor in the estimated 640 MtCO2eq/yr pan-arctic GHG source4, and an additional 6.9% contribution on top of the combined 7792 MtCO2eq/yr fossil fuel emissions from the eight Arctic nations over this time period5.

carbon↗