Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “TITRATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Comparison of the Davies and Gray titrimetric method with potassium dichromate and ceric titrants

The modified New Brunswick Laboratory (NBL) Davies and Gray titrimetry method uses potassium dichromate standard 136-f from the National Institute of Standards and Technology for calibration. However, the presence of chromium in the resulting waste stream makes the disposal of waste from this procedure costly. We report that the Actinide Analytical Chemistry (C-AAC) group at Los Alamos National Laboratory investigated and transitioned to a cerium based titrant as an alternative. We present the first long-term analytical study using this ceric-based titration method and compare it with NBL results based on the more-widely used dichromate titrimetric method.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

The complex of zinc with N-(5,6-dihydro-4H-1,3-thiazine-2-yl)benzamide

A complex of zinc with N-(5,6-dihydro-4H-1,3-thiazin-2-yl)benzamide (L) ligand, LZnCl{sub 2}, was synthesized for subsequent medical trials. The molar extinction coefficients were determined for LHBr solutions in water and physiological saline, and for LZnCl{sub 2} ethanol solution. The ligand stability in various solvents was evaluated and the value of its protonation constant was found for the physiological saline solution, logK = 5.3±0.2. The impossibility of determination of the complex stability constant by the potentiometric titration method was demonstrated. The complex exhibited an insufficient stability in aqueous and physiological saline solutions, but was stable as the solution in alcohol. There was no sorption observed upon the treatment of ligand with hydroxyapatite nanoparticles, which could be a potential carrier for the therapeutic form of LZnCl{sub 2}, providing additional degrees of freedom for the interaction of ligand with cell membranes and a prolonged action of zinc ions.

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

The Effect of Salts in Promoting Specific and Competitive Interactions between Zinc Finger Proteins and Metals

Specific protein–metal interactions (PMIs) fulfill essential functions in cells and organic bodies, and activation of these functions in vivo are mostly modulated by the complex environmental factors, including pH value, small biomolecules, and salts. Specifically, the role of salts in promoting specific PMIs and their competition among various metals has remained untapped mainly due to the difficulty to distinguish nonspecific PMIs from specific PMIs by classic spectroscopic techniques. Herein, we report Hofmeister salts differentially promote the specific PMIs by combining nanoelectrospray ionization mass spectrometry and spectroscopic techniques (fluorescence measurement and circular dichroism). Furthermore, to explore the influence of salts in competitive binding between metalloproteins and various metals, we designed a series of competitive experiments and applied to a well-defined model system, the competitive binding of zinc (II) and arsenic (III) to holo-promyelocytic leukemia protein (PML). These experiments not only provided new insights at the molecular scale as complementary to previous NMR and spectroscopic results, but also deduced the relative binding ability between zinc finger proteins and metals at the molecular scale, which avoids the mass spectrometric titration-based determination of binding constants that is frequently affected and often degraded by variable solution conditions including salt contents. .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Fundamental Studies on Poly(2-oxazoline) Side Chain Isomers Using Tandem Mass Spectrometry and Ion Mobility-Mass Spectrometry

When polymer mixtures become increasingly complex, the conventional analysis techniques become insufficient for complete characterization. Mass spectrometric techniques can satisfy this increasing demand for detailed sample characterization. Even though isobaric polymers are indistinguishable using simple mass spectrometry (MS) analyses, more advanced techniques such as tandem MS (MS/MS) or ion mobility (IM) can be used. Here, we report proof of concept for characterizing isomeric polymers, namely poly(2-n-propyl-2-oxazoline) (Pn-PrOx) and poly(2-isopropyl-2-oxazoline) (Pi-PrOx), using MS/MS and IM-MS. Pi-PrOx ions lose in intensity at higher accelerating voltages than Pn-PrOx ions during collision-induced dissociation (CID) MS/MS experiments. A Pn/i-PrOx mixture could also be titrated using survival yield calculations of either precursor ions or cation ejection species. IM-MS yielded shape differences in the degree of polymerization (DP) regions showing the structural rearrangements. Combined MS techniques are thus able to identify and deconvolute the molar mass distributions of the two isomers in a mixture. Finally, the MS/MS and IM-MS behaviors are compared for interpretation. .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Carbon mineralization and carbon dioxide emission from organic matter added soil under different temperature regimes

Purpose: Information on carbon dioxide (CO2) emission from different organic sources and their temperature sensitivity to decomposition is scarce in Bangladesh. Therefore, this study quantified the rates of CO2 emission and carbon (C) degradation constants from different organic material mixed soils at variable temperatures in two laboratory experiments. Methods: The first experiment was conducted at room temperature for 26 weeks to study CO2 emission and C mineralization using vermicompost, chicken manure, cow dung, rice straw, and rice husk biochar. Weekly CO2 emission was measured by alkali absorption followed by acid titration. The second experiment comprised two factors, viz. four organic materials (vermicompost, chicken manure, cow dung, and rice straw) and six temperature regimes (25, 30, 35, 40, 45, and 50 °C). Organic materials at 2.5 g C kg-1 soil were mixed in both experiments. Results: CO2 emission reached the peak at 5th weeks of incubation and then decreased with irregular fashion until 21st week. The C emission loss followed in the order of chicken manure > rice straw > vermicompost > cow dung > rice husk biochar, and C degradation constants indicated the slower decomposition of rice husk biochar compared to cow dung, vermicompost, chicken manure, and rice straw. Temperature positively enhanced the mineralization of organic materials in the order of 50 > 45 > 40 > 35 > 30 > 25 °C, which contributed to higher availability of soil phosphorus. Conclusions: High temperature increased mineralization of tested organic materials. Because of slower decomposition rice husk biochar, cow dung and vermicompost application can be considered as climate-smart soil management practices that might help in reducing CO2 emission from soil.

Hossain, Md. Babu (ORCID:0000000223536823)↗
DOE OSTI2020

Palladium/Zeolite Low Temperature Passive NOx Adsorbers (PNA): Structure-Adsorption Property Relationships for Hydrothermally Aged PNA Materials

Zeolites with different framework structures (SSZ-13, ZSM-5, BEA) but similar Si/Al ratios and Pd loading (~1 wr%) were synthesized and evaluated as low temperature passive NOx adsorbers (PNA). These materials exhibit high NOx adsorption efficiency with atomically dispersed Pd the active adsorption site. Hydrothermal aging at 750 ºC for 16 hours in the presence of 10% water vapor in air resulted in the formation of PdO nanoparticles in all three samples as evidenced by high energy XRD. Hydrothermal aging of the small-pore Pd/SSZ-13 (Si/Al = 6), which contain ~100-90% atomically dispersed palladium ions, decreases its PNA performance only by ~10-20%. High-field solid state 27Al NMR studies on the fresh and aged samples substantiate dealumination and significant changes in the distribution of Al (and thus, Bronsted acid) sites after hydrothermal aging. FTIR measurements with NO probe molecule and titration of Bronsted acid sites with nitrosyl (NO+) ions further corroborate the 27Al NMR data. Because framework aluminum atoms are the anchoring sites for atomically dispersed Pd ions, their elution from the framework causes the loss of active atomically dispersed Pd species. Furthermore, with the aid of HAADF-STEM imaging and synchrotron XRD studies, we further confirm and visualize the fate of these Pd species – they agglomerate into PdO nanoparticles on the external surface of zeolite. Consequently, these changes lead to the decrease in PNA performance of these materials after hydrothermal aging. The thus formed agglomerates cannot be re-dispersed back to their ionic state due to the loss of framework Al T-sites and/or inherent stability of such large PdO particles. Our study clearly demonstrates that, unlike in previous studies that found increased PNA performance upon HTA , high temperatures hydrothermal aging of PNA materials that contain atomically dispersed Pd initially, results in a decrease in NOx storage efficiency due mostly to the formation of PdO agglomerates. However, we also highlight the high hydrothermal stability of predominantly atomically dispersed 1-3 wt% Pd/SSZ-13 (Si/Al = 6), whose performance decreases only marginally after prolonged hydrothermal aging at 750 ºC. Overall, this study shows that hydrothermally stable passive NOx materials can be prepared using small-pore SSZ-13 zeolite.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Thermodynamic properties of the Nd-Bi system via emf measurements, $\mathrm{DFT}$ calculations, machine learning, and $\mathrm{CALPHAD}$ modeling

Thermodynamic properties of the Nd-Bi system were investigated using a combination of experimental measurements, first-principles calculations based on density functional theory (DFT), data mining and machine learning (DM + ML) predictions, and calculation of phase diagrams (CALPHAD) modeling. The electromotive force (emf) of Nd-Bi alloys in molten LiCl-KCl-NdCl 3 at 773–973 K was measured via coulometric titration of Nd into Bi for the determination of thermochemical properties such as activity coefficients and solubilities of Nd in Bi. A new peritectic reaction of [liquid + NdBi 2 = Nd 3 Bi 7 ] at 774 K was confirmed using differential scanning calorimetry, structural (X-ray diffraction), and microstructural (scanning electron microscopy) analyses. The unknown crystal structure of NdBi2 was suggested to be a mixture of the anti-La 2 Sb configuration and the La 2 Te-type configuration based on ML predictions for over 26,000 data-mined AB 2 -type configurations together with DFT-based verifications. Using the newly acquired experimental data and DFT-based calculations, the thermodynamic description of the Nd-Bi system was remodeled, and a more complete Nd-Bi phase diagram was calculated, including the Nd 3 Bi 7 compound, invariant transition reactions, and liquidus temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Densification and microstructure features of lithium hydride fabrication

The manufacturing of lithium hydride (LiH) utilizing uniaxial pressing, which offers fabrication with tailorable properties via microstructure control, can lead to the expansion in application of LiH while bypassing the challenges presented by historical casting manufacturing techniques. Through control of consolidation conditions such as pressure, temperature, dwell time and powder load, the presented work highlights the densification of LiH, with an emphasis on quantifying oxygen content, for applications requiring a specific density range necessary for optimized material performance. Karl Fischer Titration and X-ray Diffraction proved useful in determining oxygen and phase content while Computed Tomography and Scanning Electron Microscopy provided structural analysis. The temperature dependent densification of LiH fit with an Arrhenius term resulted in an activation energy of 21.2 kJ/mol. Images of fractured surfaces of LiH pressed at 500 °C revealed drastic grain coarsening, aided by the presence of oxygen impurities.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Elucidation of puzzling questions regarding the CrO x /Al 2 O 3 catalyst I. X-ray absorption spectroscopy aided identification of the nature of the chromium oxide species in the CrO x /Al 2 O 3 dehydrogenation catalyst system

The CATOFIN© process produces propylene from propane using a CrO x /Al 2 O 3 catalyst. Despite its use, there are still uncertainties surrounding the nature of Cr species formed during synthesis, regeneration, and aging. It has been observed that ppm levels of Cr 2 O 3 can be oxidized to Cr(VI) in air; however, when Cr 2 O 3 is in direct contact with Al 2 O 3 , Cr(VI) formation increased more than 100-fold. Here, to confirm physical contact between Cr 2 O 3 and Al 2 O 3 results in increased Cr(VI) formation, Cr 2 O 3 and Cr 2 O 3 /Al 2 O 3 samples were synthesized, calcined, and characterized. Catalytic activity measurements confirm propylene selectivity inversely tracks with Cr(VI). Wet chemical titration and X-ray absorption spectroscopy (XAS) quantified and determined the structure of the Cr(VI) species. FEFF X-ray absorption near edge structure simulations determined the potential sensitivity of the XAS to the presence of Al 3+ /Cr 3+ neighboring atoms. XAS correlated to FEFF simulations suggested that Al 3+ x Cr 3+ 2–x Cr 6+ 3 O 12 comprises a significant fraction of the Cr(VI) species formed.

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

Activity and stability of mesoporous CeO 2 and ZrO 2 catalysts for the self-condensation of cyclopentanone

Metal oxides containing acid-base pairs are widely used as catalysts for aldol condensation reactions, but they are often prone to secondary condensation and fast deactivation. In this contribution, high-surface area mesoporous CeO 2 and ZrO 2 have been synthesized and tested as catalysts for the self-condensation of cyclopentanone, an attractive molecular building block for several biomass upgrading strategies. Here, the catalytic activity, stability, and overall kinetics behavior of these two catalysts have been compared in the liquid phase. A detailed kinetics analysis shows that on both oxides, the reaction is controlled by the initial unimolecular α-H abstraction step, in which cyclopentanone forms the crucial enolate intermediate. Subsequently, the enolate couples with another cyclopentanone molecule in a bimolecular C-C coupling step. CO 2 -TPD analysis and site titration with probe molecules indicate that initially the most active catalyst is the mesoporous ZrO 2 sample with strong base character. However, this catalyst exhibits a very rapid deactivation. By contrast, the mesoporous CeO 2 prepared in this study has lower basicity strength, which results in lower initial activity, but enhanced stability.

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

Long-term stability of dithionite in alkaline anaerobic aqueous solution

Closed-system experiments were conducted to investigate the decomposition of sodium dithionite in aqueous solutions under varying pH and starting concentrations to simulate the deployment of dithionite as an in-situ redox barrier. Co-determination of dithionite and its degradation products was conducted using UV-Vis spectrometry, iodometric titration, and ion chromatography. In unbuffered solutions, dithionite reacted rapidly, whereas in near-neutral solutions (pH ~7), it persisted for ~ 50 days and in alkaline solution (pH ~9.5) for >100 days. As a result, these are the longest lifetimes reported to date, which we attribute to not only excluding oxygen but also preventing outgassing of H 2 S.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

A highly efficient catalyst of palygorskite-supported manganese oxide for formaldehyde oxidation at ambient and low temperature: Performance, mechanism and reaction kinetics

A series of palygorskite-supported manganese oxide (MnO x /PG) catalysts were prepd. by a pptn. method using different manganese precursor. The as-prepared MnO x /PG catalysts were used to evaluate the catalytic oxidn. of HCHO and characterized by BET, XRD, TG, Raman spectroscopy, TEM, H 2 -TPR, XPS, and chemical titration. The results showed that the crystalline phase, distribution and Mn valence states of MnO x on the surface of PG depended on the precursors. Birnessite-type manganese oxide (δ-MnO 2 ) formed and uniformly coated on the surface of PG when potassium permanganate (PP) was used as the precursor. The MnO x /PG-PP catalyst showed the best catalytic activity for HCHO removal at low temp. among these catalysts and achieved complete HCHO conversion at 150 °C. More importantly, the dynamic single-pass removal efficiency of MnO x /PG-PP catalyst for ppm-level HCHO oxidn. was as high as 95% under high GHSV (300 L/g·h) at ambient temp. MnO x /PG-PP catalyst also exhibited excellent cycling stability and long-term activity at low and ambient temp. The kinetic results of MnO x /PG-PP catalyst showed that the oxidn. of HCHO followed the Mars-van Krevelen mechanism. The possible reaction pathway of HCHO oxidn. was proposed based on in situ DRIFTS and TPSR studies. The large sp. surface area, highly distributed active component, a high proportion of Mn 4+ species, and lattice oxygen content are responsible for the high catalytic activity of MnO x /PG-PP for oxidn. of formaldehyde. This work developed a natural mineral supported manganese oxide as an inexpensive and efficient catalyst for the purifn. of HCHO in industrial or indoor air environment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Ambient pressure X-ray photoelectron spectroscopy study of room-temperature oxygen adsorption on Cu(1 0 0) and Cu(1 1 1)

We investigated the room-temperature chemisorption of oxygen on Cu(1 0 0) and Cu(1 1 1) using ambient-pressure X-ray photoelectron spectroscopy (APXPS). A shoulder-to-shoulder comparison between the oxygen-gas titration on the two surfaces reveals that Cu(1 0 0) is the more active for oxygen dissociative chemisorption when the surfaces are clean. The (2 $\sqrt{2}$ × $\sqrt{2}$)R45o missing-row reconstruction appears in Cu(1 0 0)’s LEED image after about 10 4 Langmuir of oxygen exposure, whereas on Cu(1 1 1), no long-range ordering was observed throughout the whole experiment. An oxide layer consisting of cuprous and cupric oxide shows up on Cu(1 1 1) at an oxygen exposure that is significantly lower than for Cu(1 0 0). This observation suggests that the presence of (2 $\sqrt{2}$ × $\sqrt{2}$)R45o missing-row reconstruction layer slows down Cu(1 0 0) oxidation. Literature has widely reported that surface morphology influences the copper oxidation process. This study provides an XPS demonstration that copper surface oxide formation in O 2 at room temperature depends on the surface crystallographic orientation.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Understanding how defects and dopant atoms in copper surface oxides affect reactivity

Copper and its oxides are key catalytic materials, on which reactions often occur at the metal/oxide interface. Here, in this work, we directly connect the induction period observed during methanol-driven reduction of thin-film copper oxides to their atomic-scale structural order. Using temperature-programmed desorption (TPD) methanol titrations combined with scanning tunneling microscopy, we show that highly ordered oxide phases – particularly the “29” structure with its low defect density – exhibit long induction periods and initially low reactivity. The induction period, defined as the number of methanol TPD cycles required to reach half of the maximum formaldehyde yield, scales with oxide order and oxygen coverage. Enhanced reactivity of well-ordered oxides emerges only after repeated methanol adsorption/desorption cycles generate oxygen vacancies and new Cu(111)/Cu x O interfacial sites. In contrast, disordered or sub-stoichiometric oxides, which contain more intrinsic defects and interfaces, are active from the first TPD cycle. We further examine how dilute Pt and Rh dopants influence oxide order and reactivity: 1% Pt increases defect density and catalytic activity, while 1% Rh promotes oxide ordering and longer induction periods. These findings demonstrate that dilute alloying provides a potential method for tuning the structure and reactivity of Cu(111)/Cu x O interfaces.

Cu(111)Methanol oxidation↗
DOE OSTI2016

Arsenic and 17-β-estradiol bind to each other and neutralize each other’s signaling effects

We report that arsenic trioxide (ATO) and 17-beta-estradiol (E2) abolish each other’s independent cell signaling effects in respect of cell survival and proliferation/migration of breast cancer (MCF-7) cells. The possibility that this is due to binding of ATO to E2 was confirmed through difference absorption spectroscopy, chromatography-coupled voltammometry and 1-D {sup 1}H and {sup 13}C NMR spectroscopy. Binding leads to attenuation of E2’s hydroxyl {sup 1}H peaks at its C17 and C3 carbon positions. The results suggest that ATO and E2 can titrate each other’s levels, potentially explaining why sustained arsenic exposure tends to be associated with delays in age of menarche, advanced age of menopause, poorer sperm quality, higher overall morbidity in men, and lower incidences of breast cancer in women in some arsenic-contaminated areas. - Highlights: • Difference absorption spectroscopy suggests that arsenic binds to estradiol. • Interaction with arsenic alters {sup 1}H and {sup 13}C NMR spectra of estradiol at positions C3 and C17. • Estradiol traps arsenic on C{sub 18} reverse-phase columns. • Estradiol and arsenic neutralize each other’s ability to stimulate scratch wound healing. • Arsenic appears to form pnictogen bonds with hydroxyls on estradiol.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Suramin blocks interaction between human FGF1 and FGFR2 D2 domain and reduces downstream signaling activity

The extracellular portion of the human fibroblast growth factor receptor2 D2 domain (FGFR2 D2) interacts with human fibroblast growth factor 1 (hFGF1) to activate a downstream signaling cascade that ultimately affects mitosis and differentiation. Suramin is an antiparasiticdrug and a potent inhibitor of FGF-induced angiogenesis. Suramin has been shown to bind to hFGF1, and might block the interaction between hFGF1 and FGFR2 D2. Here, we titrated hFGF1 with FGFR2 D2 and suramin to elucidate their interactions using the detection of NMR. The docking results of both hFGF1-FGFR2 D2 domain and hFGF1-suramin complex were superimposed. The results indicate that suramin blocks the interaction between hFGF1 and FGFR2 D2. We used the PyMOL software to show the hydrophobic interaction of hFGF1-suramin. In addition, we used a Water-soluble Tetrazolium salts assay (WST1) to assess hFGF1 bioactivity. The results will be useful for the development of new antimitogenic activity drugs. - Highlights: • The interfacial residues on hFGF1-FGFR2 D2 and hFGF1-Suramin contact surface were mapped by {sup 1}H-{sup 15}N HSQC experiments. • hFGF1-FGFR2 D2 and hFGF1-Suramin complex models were generated from NMR restraints by using HADDOCK program. • We analyzed hFGF1-Suramin complex models and found the interaction between hFGF1-Suramin is hydrophobic. • The bioactivity of the hFGF1-FGFR2 D2 and hFGF1-Suramin complex was studied by using WST1 assay.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

The Mycobacterium tuberculosis desaturase DesA1 (Rv0824c) is a Ca{sup 2+} binding protein

The hallmark feature of Mycobacterium tuberculosis (M.tb) the causative agent of human tuberculosis, is its complex lipid rich cell wall comprised primarily of mycolic acids, long chain fatty acids that play a key role in structural stability and permeability of the cell wall. In addition, they are involved in inhibiting phagosome-lysosome fusion and aid in granuloma formation during the pathogenic process. M.tb DesA1 is an essential acyl-acyl carrier protein desaturase predicted to catalyze the introduction of position specific double bonds during the biosynthesis of mycolic acids. This protein is one among three annotated desaturases (DesA1-3) in the M.tb genome but is unique in containing a βγ-crystallin Greek key signature motif, a well-characterized fold known to mediate Ca{sup 2+} binding in both prokaryotic and eukaryotic organisms. Using Isothermal Titration Calorimetry and {sup 45}CaCl{sub 2} overlay, we demonstrate that Ca{sup 2+} binds to DesA1. Spectroscopic measurements suggested that this binding induces changes in protein conformation but does not lead to significant alterations in the secondary structure of the protein, a feature common to several βγ-crystallins. An M. smegmatis strain over-expressing M.tb desA1 showed a Ca{sup 2+} dependent variation in surface phenotype, revealing a functional role for Ca{sup 2+}in DesA1 activity. This study represents the first identification of a Ca{sup 2+} binding βγ-crystallin in M.tb, emphasizing the implicit role of Ca{sup 2+} in the pathogenesis of M.tb. - Highlights: • Mycobacterium tuberculosis DesA1 is an essential acyl-ACP desaturase. • DesA1 was identified to contain a βγ-crystallin Greek key signature motif. • Ca{sup 2+} binds to DesA1 with an affinity of 53 μM and induces changes in its conformation. • M. smegmatis overexpressing M.tb DesA1 shows a Ca{sup 2+} dependent phenotype. • Targetting the Ca{sup 2+} dependent function of DesA1 could be of therapeutic value.

60 APPLIED LIFE SCIENCES↗