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At least 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Preparation and Characterization of Iminodiacetate Group Containing Nonwoven Polyethylene Fabrics and Its Application in Chromium Adsorption

An iminodiacetate (IDA) group containing nonwoven polyethylene (PE) film was prepared by radiation induced graft polymerization of an epoxy group containing monomer, glycidyl methacrylate (GMA) onto nonwoven PE fabric and subsequent chemical modification to IDA group. The effect of solvents (water, methanol, ethanol, isopropyl alcohol and dimethyl sulfoxide) on modification of epoxy group of GMA grafted PE (GMA-g-PE) fabric to IDA group was investigated. Ethanol provided a higher density of IDA group on GMA-g-PE fabric. Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and dynamic mechanical analysis of IDA-GMA-PE adsorbent, GMA-g-PE fabric and pure PE fabric were studied. The ability of resultant IDA adsorbent to absorb chromium from aqueous medium was evaluated by batch method. The parameters such as feeding chromium concentration, pH of chromium solution and adsorption time of IDA adsorbent were discussed. The obtained results illustrate that the IDA adsorbent could be fruitful to absorb chromium from water. The equilibrium experimental data for the adsorption of chromium on IDA adsorbent fitted Langmuir isotherm model.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Optimization of Beidellite/Polyaniline Production Conditions by Central Composite Design for Removal of Acid Yellow 194

In the adsorption process, the adsorbent structure and its interaction with wastewater are the main determinant of the process efficiency. For this reason, the correct selection of the production conditions for the produced adsorbents is critical. In this study, the reaction time and the concentration of acid, oxidant, substrate, and monomer were selected as independent variables which effect the structure of the polyaniline based composite material. These production variables of polyaniline/beidellite (PANI/BEI) composites were designed by response surface methodology (RSM). According to RSM, 46 different PANI/BEI composites were synthesized and were used as an adsorbent in the removal of acid yellow 194. Thus, the optimum PANI/BEI production conditions were determined. After the identification of the optimum PANI/BEI production conditions, the effect of adsorption conditions such as pH, mixing time, and dye concentration were studied by batch experiments. The maximum adsorption capacity was obtained as 123 (mg g{sup −1}) at the T = 25 °C, t = 24 h, pH 3, m{sub s} = 0.15 g adsorbent, V{sub s} = 50 ml dye solution, and ω = 200 rpm. The results presented in this study revealed that the central composite design is a suitable method to optimize the production conditions of PANI/BEI and the prepared PANI/BEI composites has an important potential as an adsorbent for the removal of metal-complex dyes such as AY194. In addition, the polymerization of aniline and the removal of dye were confirmed by different analytical techniques such as BET, XRD, SEM, and EDAX.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

A Novel Wastewater Treating Material: Cationic Poly Acrylamide/Diatomite Composite Flocculant

In this work, poly(methacrylatoethyl trimethyl ammonium chloride -co-acrylamide)/diatomite composite flocculant was synthesized via in situ polymerization in aqueous solution and applied in waste water treatment. The structure of composite flocculants was characterized by FT-IR, {sup 1}HNMR and XRD, TGA and viscometer. Herein, the apparent viscosity of composite flocculants was employed as comparison standard of their performance to evaluate the influence of the reaction parameters, such as monomer feeding ratio, diatomite mass fraction and polymerization temperature, etc. on their flocculation performance. And based on the above investigations, the optimum synthesis condition could be found. By comparing flocculation properties of composite flocculants with that of the conventional cationic flocculant, the dosage of composite flocculant that could make the transmittance of treated waste water exceed 95 % was only 7.5 ppm which was far lower than that of conventional flocculant (60–90 ppm). Meanwhile, the settling time was lower than 5 s which was similarly to that of conventional flocculant. Finally, the conclusion was that the composite flocculant owned higher absorption capacity and larger chain extending space than those of conventional linear flocculant due to the introduction of diatomite as backbone, which could make linear polymer chains free from entanglement and improve the flocculation capacity notably.

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

Novel Biocomposites Based on Sunflower Oil and Alfa Fibers as Renewable Resources

The aim of this work is to develop biocomposites based on modified sunflower oil as resin and short natural fibers from Alfa plants (Stipa tenacissima) as reinforcement. Epoxidized sunflower oil (ESFO) was chemically modified via acrylation reaction to obtain acrylated epoxidized sunflower oil resin (AESFO). The AESFO resin was then copolymerized with styrene as co-monomer in the presence of boron trifluoride (BF{sub 3}) as cationic initiator and cobalt octoate (Co) as catalyst. Experimental conditions of this modification were optimized by varying styrene, Co and BF{sub 3} wt%. The styrene was varied from 30, 40 to 50 wt% while the catalyst (Co) was varied from 0, 0.01, 0.02 to 0.03 wt%. Two different percents of BF{sub 3} were considered: 0.5 and 1 wt%. The prepared samples were evaluated according to their appearance and then characterized in terms of tensile properties (stress at break, Young’s modulus and elongation at break) to determine the best ratio of styrene/BF{sub 3}/Co. Alfa fibers, used as bio-reinforcement, were treated with a 5% NaOH solution and characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermo gravimetric analysis (TGA). Biocomposites were prepared by using untreated (UAF) and treated Alfa fibers (TAF) at a ratio of 5 wt% and characterized in terms of tensile properties and morphology by SEM. The best results were obtained with TAF. Then, the ratio of TAF was varied (5, 7.5 and 10 wt%) and the tensile and thermal properties of the biocomposites were characterized. The results showed that the best results were obtained with the ratio of 7.5 wt%.

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

Conferring Antibacterial Properties on Sesbania Gum via Microwave-Assisted Graft Copolymerization of DADMAC

Microbial contamination, the consequences of both anthropogenic and geogenic activity, includes high health and environmental threats and may adversely affects the ecological niche. The present work is a successful attempt towards the fabrication of anti-bacterial agent by incorporation of cationic monomer, diallyldimethylammonium chloride (DADMAC) on sesbania gum through microwave assisted method. The grafted chains of poly (DADMAC) provide positive charge to sesbania gum which in turn confers antibacterial activity. The synthesized product was characterized through FTIR, SEM, TGA, DSC elemental and viscometric analysis. The inhibitory activity of the synthesized product has been evaluated in vitro against both Gram-positive (Staphylococcus aureus NCIM 2122 and Bacillus anthracis) as well as Gram-negative (Salmonella typhi NCIM 2501 and Escherichia coli NCIM 2832) bacteria through standard agar cup method. Optimum minimum inhibitory concentration for each grade of graft copolymer measured by calculating the zone of inhibition has been found at 750 µg/ml. Graphical Abstract: .

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Synthesis Approaches and Morphological Properties on Dielectric Enhancement and Microwave Absorption of Fe{sub 3}O{sub 4}/PANI Nanocomposites

In the present work, Fe{sub 3}O{sub 4} spherical (Fe{sub 3}O{sub 4}-cop) and raspberry-like (Fe{sub 3}O{sub 4}-hyd) nanoparticles were synthesized via co-precipitation and hydrothermal routes, respectively. Fe{sub 3}O{sub 4}/polyaniline (PANI) nanocomposites were prepared by in situ oxidative polymerization of aniline monomer in the presence of the Fe{sub 3}O{sub 4} materials. Characterization of the nanocomposites by XRD, FT-IR, FESEM, and TEM techniques revealed a core/shell structure for Fe{sub 3}O{sub 4}-hyd/PANI, unlike the PANI blocks with embedded Fe{sub 3}O{sub 4} and γ-Fe{sub 2}O{sub 3} observed in Fe{sub 3}O{sub 4}-cop/PANI composites. The larger and pure magnetite nanoparticles produced with the hydrothermal process and the respective nanocomposite with PANI possess higher magnetization and coercivity values, according to the magnetic investigation with VSM. Moreover, according to the electromagnetic characterization in the X-band, the Fe{sub 3}O{sub 4}-hyd/PANI nanocomposite exhibits the highest complex permittivity level, as a consequence of increased interfacial polarization in the Fe{sub 3}O{sub 4}-hyd/PANI system. On this account, reflection loss measurements have shown the superior microwave absorption capability of Fe{sub 3}O{sub 4}-hyd/PANI composite, compared with Fe{sub 3}O{sub 4}-cop/PANI, with a measured maximum of −31.28 dB at 8.5 GHz for 3.5 mm layer thickness.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Cobalt and manganese complexes with redox-active ligands in polymerization of acrylonitrile and methyl methacrylate

The influence of bis[4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-o-iminobenzosemiquinonato]cobalt(II) and 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinonato]-[4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-amidophenolate]manganese(III) on polymerization of methyl methacrylate and acrylonitrile in the presence of azobisisobutyronitrile (as a traditional radical initiator) and alkyl halides (used for initiation of controlled atom transfer radical polymerization process) was studied. The effect of the nature of the activating agents (amines) and the temperature conditions on the overall polymerization rate of the indicated monomers, as well as molecular weight characteristics of the synthesized polymers, were analyzed. The optimal conditions for the synthesis of polyacrylonitrile and poly(methyl methacrylate) with a relatively narrow molecular weight distribution were selected.

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

Stabilization of dinitrosyl iron complexes under matrix isolation conditions: solvent and polymer effects on the synthesis of composites based on poly(methyl methacrylate) and iron complexes [Fe{sub 2}(μ-NCS-R){sub 2}(NO){sub 4}]

Homogeneous composites based on poly(methyl methacrylate) and its copolymers with methacrylic acid and on the nitrosyl iron complexes with 2-mercaptobenzimidazole and 2-mercaptobenzthiazole were synthesized. An analysis of the experimental data obtained by the methods of small-angle X-ray diffraction and SQUID magnetometry in combination with the results of quantum chemical calculations showed that the nitrosyl complexes did not retain their initial binuclear structure under the matrix isolation conditions: some complexes decompose to mononuclear ones. The percentage ratio of the dimers and monomers depends on the fraction of the methacrylic acid copolymer in the polymeric matrix and is almost independent of the type of thiol ligand in the iron complex.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

A new approach to the study of the structure of polyisoprene obtained by cationic polymerization

The use of the T{sub 2} filter in NMR studies allowed us to separate carbon atoms by their mobility in different fragments of the macromolecular chain of polyisoprene synthesized by cationic polymerization. The NMR signals of terminal units with conjugated double bonds were identified for the first time for the “cationic” polyisoprene, which experimentally confirmed the transfer of the growing chain to the monomer in the process of cationic polymerization of isoprene.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Efficient Production of Polymalic Acid by a Novel Isolated Aureobasidium pullulans Using Metabolic Intermediates and Inhibitors

Polymalic acid (PMA) is a linear anionic polyester composed of L-malic acid monomers, which have potential applications as drug carriers, surgical suture, and biodegradable plastics. In this study, a novel strain of Aureobasidium pullulans var. melanogenum GXZ-6 was isolated and identified according to the morphological observation and deoxyribonucleic acid internal-transcribed spacer sequence analysis, and the product of PMA was characterized by FT-IR, {sup 13}C-NMR, and {sup 1}H-NMR spectra. The PMA titer of GXZ-6 reached 62.56 ± 1.18 g L{sup −1} with productivity of 0.35 g L{sup −1} h{sup −1} using optimized medium with addition of metabolic intermediates (citrate and malate) and inhibitor (malonate) by batch fermentation in a 10-L fermentor. Besides that the malate for PMA synthesis in GXZ-6 might mainly come from the glyoxylate cycle, based on results, citrate, malate, malonate, and maleate increased while succinate and fumarate inhibited the production of PMA, which was different from that of other A. pullulans. This study provided a potential strain and a simple metabolic control strategy for high-titer production of PMA and shared novel information on the biosynthesis pathway of PMA in A. pullulans.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Probing Conformational Dynamics of Tau Protein by Hydrogen/Deuterium Exchange Mass Spectrometry

Fibrillization of the microtubule-associated protein tau has been recognized as one of the signature pathologies of the nervous system in Alzheimer’s disease, progressive supranuclear palsy, and other tauopathies. The conformational transition of tau in the fibrillization process, tau monomer to soluble aggregates to fibrils in particular, remains unclear. Here we report on the use of hydrogen/deuterium exchange mass spectrometry (HDX-MS) in combination with other biochemical approaches, including Thioflavin S fluorescence measurements, enzyme-linked immunosorbent assay (ELISA), and Western blotting to understand the heparin-induced tau’s fibrillization. HDX-MS studies including anti-tau antibody epitope mapping experiments provided molecular level details of the full-length tau’s conformational dynamics and its regional solvent accessibility upon soluble aggregates formation. The results demonstrate that R3 region in the full-length tau’s microtubule binding repeat region (MTBR) is stabilized in the aggregation process, leaving both N and C terminal regions to be solvent exposed in the soluble aggregates and fibrils. The findings also illustrate the practical utility of orthogonal analytical methodologies for the characterization of protein higher order structure. .

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

The Metal Effect on Self-Assembling of Oxalamide Gelators Explored by Mass Spectrometry and DFT Calculations

Gels formed by self-assembly of small organic molecules are of wide interest as dynamic soft materials with numerous possible applications, especially in terms of nanotechnology for functional and responsive biomaterials, biosensors, and nanowires. Four bis-oxalamides were chosen to show if electrospray ionization mass spectrometry (ESI-MS) could be used as a prediction of a good gelator and also to shed light on the gelation processes. By inspecting the gelation of several solvent, we showed that bis(amino acid)oxalamide 1 proved to be the most efficient, also being able of forming the largest observable assemblies in the gas phase. The formation of singly charged assemblies holding from one up to six monomer units is the outcome of the strong intermolecular H-bonds, particularly among terminal carboxyl groups. The variation of solvents from polar aprotic towards polar protic did not have any significant effects on the size of the assemblies. The addition of a salt such as NaOAc or Mg(OAc){sub 2}, depending on the concentration, altered the assembling. Computational analysis at the DFT level aided in the interpretation of the observed trends and revealed that individual gelator molecules spontaneously assemble to higher aggregates, but the presence of the Na{sup +} cation disrupts any gelator organization since it becomes significantly more favorable for gelator molecules to bind Na{sup +} cations up to the 3:1 ratio than to self-assemble, being fully in line with experimental observations reported here. .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Crystal structures of type III{sub H} NAD-dependent D-3-phosphoglycerate dehydrogenase from two thermophiles

Highlights: • Determined the crystal structures of PGDH from two thermophiles. • Monomer is composed of nucleotide binding domain and substrate binding domain. • Crystal structures of type III{sub H} PGDH. - Abstract: In the L-Serine biosynthesis, D-3-phosphoglycerate dehydrogenase (PGDH) catalyzes the inter-conversion of D-3-phosphoglycerate to phosphohydroxypyruvate. PGDH belongs to 2-hydroxyacid dehydrogenases family. We have determined the crystal structures of PGDH from Sulfolobus tokodaii (StPGDH) and Pyrococcus horikoshii (PhPGDH) using X-ray diffraction to resolution of 1.77 Å and 1.95 Å, respectively. The PGDH protomer from both species exhibits identical structures, consisting of substrate binding domain and nucleotide binding domain. The residues and water molecules interacting with the NAD are identified. The catalytic triad residues Glu-His-Arg are highly conserved. The residues involved in the dimer interface and the structural features responsible for thermostability are evaluated. Overall, structures of PGDHs with two domains and histidine at the active site are categorized as type III{sub H} and such PGDHs structures having this type are reported for the first time.

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

Amyloid β oligomers induce interleukin-1β production in primary microglia in a cathepsin B- and reactive oxygen species-dependent manner

Amyloid β (Aβ) peptide, a causative agent of Alzheimer's disease, forms two types of aggregates: oligomers and fibrils. These aggregates induce inflammatory responses, such as interleukin-1β (IL-1β) production by microglia, which are macrophage-like cells located in the brain. In this study, we examined the effect of the two forms of Aβ aggregates on IL-1β production in mouse primary microglia. We prepared Aβ oligomer and fibril from Aβ (1–42) peptide in vitro. We analyzed the characteristics of these oligomers and fibrils by electrophoresis and atomic force microscopy. Interestingly, Aβ oligomers but not Aβ monomers or fibrils induced robust IL-1β production in the presence of lipopolysaccharide. Moreover, Aβ oligomers induced endo/phagolysosome rupture, which released cathepsin B into the cytoplasm. Aβ oligomer-induced IL-1β production was inhibited not only by the cathepsin B inhibitor CA-074-Me but also by the reactive oxygen species (ROS) inhibitor N-acetylcysteine. Random chemical crosslinking abolished the ability of the oligomers to induce IL-1β. Thus, multimerization and fibrillization causes Aβ oligomers to lose the ability to induce IL-1β. These results indicate that Aβ oligomers, but not fibrils, induce IL-1β production in primary microglia in a cathepsin B- and ROS-dependent manner. - Highlights: • We prepared amyloid β (Aβ) fibrils with minimum contamination of Aβ oligomers. • Primary microglia (MG) produced IL-1β in response to Aβ oligomers, but not fibrils. • Only Aβ oligomers induced leakage of cathepsin B from endo/phagolysosomes. • IL-1β production in response to Aβ oligomers depended on both cathepsin B and ROS. • Crosslinking reduced the ability of the Aβ oligomers to induce IL-1β from MG.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

α-Synuclein aggregation, seeding and inhibition by scyllo-inositol

Recent literature demonstrates the accelerated aggregation of α-synuclein, a protein implicated in the pathogenesis of Parkinson's disease (PD), by the presence of preformed fibrillar conformers in vitro. Furthermore, these preformed fibrillar seeds are suggested to accelerate pathological induction in vivo when injected into the brains of mice. Variation in the results of in vivo studies is proposed to be caused by α-synuclein conformational variants. To investigate the impact of amino acid sequence on seeding efficiency, human and mouse α-synuclein seeds, which vary at 7 amino acid residues, were generated and cross-seeding kinetics studied. Using transmission electron microscopy (TEM), we confirmed that mouse α-synuclein aggregated more rapidly than human α-synuclein. Subsequently, we determined that seeding of human and mouse α-synuclein was more rapid in the presence of seeds generated from the same species. In addition, an established amyloid inhibitor, scyllo-inositol, was examined for potential inhibitory effects on α-synuclein aggregation. TEM analysis of protein:inhibitor assays demonstrated that scyllo-inositol inhibits the aggregation of α-synuclein, suggesting the therapeutic potential of the small molecule in PD. - Highlights: • Mouse α-syn fibrillizes in a significantly shorter timeframe than human α-syn. • Seeding of monomers is more efficient when seeds originate from the same species. • scyllo-Inositol has anti-aggregation effects on mouse and human α-syn.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Crystal structure analysis of a hypothetical protein (MJ0366) from Methanocaldococcus jannaschii revealed a novel topological arrangement of the knot fold

The crystal structure of a hypothetical protein MJ0366, derived from Methanocaldococcus jannaschii was solved at 1.9 Å resolution using synchrotron radiation. MJ0366 was crystallized as a monomer and has knot structural arrangement. Intriguingly, the solved structure consists of novel ‘KNOT’ fold conformation. The 3{sub 1} trefoil knot was observed in the structure. The N-terminal and C-terminal ends did not participate in knot formation. - Highlights: • Crystal structure of a hypothetical protein from Methanocaldococcus jannaschii was determined. • The protein adopts novel knot fold conformation. • Structure of the first smallest knot protein was solved.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Lipid production from non-sugar compounds in pretreated lignocellulose hydrolysates by Rhodococcus jostii RHA1

Valorization of all carbon sources from biorefinery wastes to biofuels and bioproducts is an attractive but challenging strategy to improve the carbon efficiency of the entire biorefinery process for economic competitiveness. Rhodococcus jostii RHA1 is considered as a promising candidate for conversion of non-sugar compounds in pretreated lignocellulose hydrolysate, which contain aromatic monomers, furans and acids derived from biomass. However, the insufficient understanding of the strain’s complex metabolism network limits its application. In this study, furans (furfural, 5-hydroxymethylfurfural), phenols (vanillin, vanillate), and organic acids (acetic acid), which mimic the complex components of the non-sugar compounds in pretreated biomass hydrolysate, were mixed with benzoate or used individually as carbon sources to investigate the growth and lipid accumulation of R. jostii RHA1. Fermentation kinetics, specific growth rates (h-1) and lipid yield (g(g) -1, g(mmol)-1), for each selected biomass-derived compound were compared for lipid production. The order of the specific growth rates (h-1) was benzoate > acetic acid > vanillate > vanillin. Higher consumption rate of benzoate than that of vanillate, as well as different lipid yield from them, suggested the preference of strain employing two branches of ß-ketoadipate pathway and plausibly distinct carbon routing to lipid biosynthesis. And acetic acid showed the lowest lipid yield (g(mmol)-1) indicating less carbon contributed to lipid production. The highest lipid content (0.46 g lipid/g CDW) was achieved using benzoate as a main carbon source in the presence of 5-hydroxymethylfurfural (5-HMF). The generated lipids predominantly contained C16:0 and C17:0 fatty acids. The concentration of furfural and 5-HMF in fermentation broth decreased individually or simultaneously with benzoate catabolism. NMR results revealed the oxidation of furfural and 5-HMF by R. jostii RHA1. This study provides new insights into the catabolism and metabolism of non-sugar compounds derived from biomass by Rhodococcus in terms of growth and lipid production, facilitating its application to 2nd generation biofuel production.

Li, Xiaolu↗
DOE OSTI2014

Ion-specific effects influencing the dissolution of tricalcium silicate

It has been recently demonstrated that the dissolution kinetics of tricalcium silicate (C{sub 3}S) is driven by the deviation from its solubility equilibrium. In this article, special attention is paid to ions relevant in cement chemistry likely to interact with C{sub 3}S. In order to determine whether specific effects occur at the interface C{sub 3}S–water, particular efforts have been made to model ion activities using Pitzer's model. It has been found that monovalent cations and monovalent anions interact very little with the surface of C{sub 3}S. On the other side, divalent anions like sulfate slow down the dissolution more strongly by modifying the surface charging of C{sub 3}S. Third, aluminate ions covalently bind to surface silicate monomers and inhibit the dissolution in mildly alkaline conditions. The formation and the breaking of these bonds depend on pH and on [Ca{sup 2+}]. Thermodynamic calculations performed using DFT combined with the COSMO-RS solvation method support the experimental findings.

36 MATERIALS SCIENCE↗