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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Carbonate “clumped” isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near-constant temperature, salinity, and pH and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop “clumped” isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate-related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly substituted isotopologue 13 C 18 O 16 O 2 in carbonate minerals, analyzed in CO 2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ 47 values. We analyzed Δ 47 in live-collected aragonitic scleractinian ( Enallopsammia sp.) and high-Mg calcitic gorgonian (Isididae and Coralliidae) deep-sea corals and compared results to published data for other aragonitic scleractinian taxa. Measured Δ 47 values were compared to in situ temperatures, and the relationship between Δ 47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than high-Mg calcitic gorgonian corals and the two groups of coral produce statistically different relationships between Δ 47 –temperature calibrations. These data are significant in the interpretation of all carbonate clumped isotope calibration data as they show that distinct Δ 47 –temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO 2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset between the corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect high-Mg and aragonite crystals attaining nominal mineral equilibrium clumped isotope signatures due to conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological “vital effect” influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological vital effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO 2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on Δ 47 is a subject that warrants further investigation.

58 GEOSCIENCES↗
DOE OSTI2021

Potential Dependent Mn Oxidation and Its Role in Passivation of Ni 38 Fe 20 Cr 22 Mn 10 Co 10 Multi-Principal Element Alloy Using Multi-Element Resolved Atomic Emission Spectroelectrochemistry

The identity of passivating oxides on multi-principal element alloys is of great interest as their optimization offers the potential for exceptional corrosion resistance in aqueous solutions over a broad range of potential and pH. This study focuses on a non-equiatomic Ni 38 Fe 20 Cr 22 Mn 10 Co 10 solid solution alloy and tracks the fate of each alloying element during linear sweep voltammetry, low and intermediate potential holds in the passive potential domain as well as during open circuit relaxation after anodic polarization in slightly acidified Cl − solution. Ni dissolves at all potentials investigated in this work, Fe and Co are incorporated into oxides or hydroxides in low concentrations whilst Cr and Mn are enriched at passive potentials. At low passivating potentials, Mn(II) dissolves and is incorporated in minor amounts in oxides containing large concentrations of Cr(III). Considerable enrichment in Mn(II)-species occurs relative to Cr(III) in the oxide at 0.1 V vs SCE. Electrochemical impedance spectroscopy suggests the presence of layered oxides with marginal passivation at high Mn(II) levels. The formation of these oxides depends on a combination of thermodynamic and kinetic factors as well as the sequence of passivation.

Han, Junsoo (ORCID:0000000192952954)↗
DOE OSTI2019

Electrochemical Behavior of Steel in Concrete Under Wet and Dry Condition with NaCl Solution

The corrosion of steel and environmental factors in concrete under the wet and dry condition were examined by using electrochemical impedance spectroscopy (EIS) and microelectrode sensors. The concentration of chloride ion (CL) was detected by Ag/AgCl microelectrode, and the pH was monitored by W/WO{sub x} one. The CL increased step by step according to the wet and dry condition. Besides, the cathodic current of the oxygen (I{sub O{sub 2}}) was increased just after the immersion of concrete sample in wet process. These behaviors were thought to promote the corrosion of steel. From EIS, the rust was formed and destroyed on the surface of steel in concrete under the wet and dry condition. It was quantitatively demonstrated by monitoring that the corrosion of steel started when CL exceeded the threshold value in concrete under the wet and dry condition.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Release and control of hydrogen sulfide during sludge thermal drying

The release of hydrogen sulfide (H2S) during sludge drying is a major environmental problem because of its toxicity to human health. A series of experiments were performed to investigate the mechanisms and factors controlling the H2S release. Results of this study show that: 1) the biomass and activity of sulfate-reducing bacteria (SRB) in sludge were the major factors controlling the amount of H2S release, 2) the sludge drying temperature had an important effect on both the extent and the timing of H2S release from the sludge, and 3) decreasing sludge pH increased the H2S release. Based on the findings from this study, a new system that integrates sludge drying and H2S gas treatment was developed to reduce the amount of H2S released from sludge treatments.

sludge, H2S, treatment, drying, control↗
DOE OSTI2014

Millimeter/submillimeter spectroscopy of PH{sub 2}CN ( X-tilde {sup 1}A') and CH{sub 3}PH{sub 2} ( X-tilde {sup 1}A'): probing the complexity of interstellar phosphorus chemistry

Millimeter/submillimeter spectra of PH{sub 2}CN ( X-tilde {sup 1}A') and CH{sub 3}PH{sub 2} ( X-tilde {sup 1}A') have been recorded for the first time using direct absorption techniques. This work extends previous measurements of both molecules beyond the 10-50 GHz range. Both species were created in the presence of an AC discharge by the reaction of phosphorus vapor and either cyanogen and hydrogen (PH{sub 2}CN) or methane (CH{sub 3}PH{sub 2}). Twelve rotational transitions of PH{sub 2}CN were recorded over the region 305-422 GHz for asymmetry components K{sub a} = 0 through 8. For CH{sub 3}PH{sub 2}, eight rotational transitions were measured from 210-470 GHz with K{sub a} = 0 through 16; these spectra exhibited greater complexity due to the presence of internal rotation, which splits the K{sub a} = 1, 2, and 3 asymmetry components into A and E states. Combined analyses of the millimeter/submillimeter and previous microwave data were performed for both molecules. For PH{sub 2}CN, the spectra were fit with a Watson S-reduced asymmetric top Hamiltonian, resulting in more accurate rotational and centrifugal distortion constants. In the case of CH{sub 3}PH{sub 2}, an asymmetric top internal-rotation Hamiltonian was employed in the analysis, significantly improving the rotational and torsional parameters over previous microwave estimates. Searches for both molecules were subsequently conducted toward Sgr B2(N), using the 12 m telescope of the Arizona Radio Observatory (ARO). Neither species was identified, with abundance upper limits, relative to H{sub 2}, of f (PH{sub 2}CN/H{sub 2}) < 7.0 × 10{sup –12} and f (CH{sub 3}PH{sub 2}/H{sub 2}) < 8.4 × 10{sup –12}. The nitrogen analogs NH{sub 2}CN and CH{sub 3}NH{sub 2} are therefore more abundant in Sgr B2(N) by factors of >2 and >200, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2008

Remote Sensing of the Absorption Coefficients and Chlorophyll a Concentration in the U.S. Southern Middle Atlantic Bight from SeaWiFS and MODIS-Aqua

At present, satellite remote sensing of coastal water quality and constituent concentration is subject to large errors as compared to the capability of satellite sensors in oceanic waters. In this study, field measurements collected on a series of cruises within U.S. southern Middle Atlantic Bight (SMAB) were applied to improve retrievals of satellite ocean color products in order to examine the factors that regulate the bio-optical properties within the continental shelf waters of the SMAB. The first objective was to develop improvements in satellite retrievals of absorption coefficients of phytoplankton (a(sub ph)), colored dissolved organic matter (CDOM) (a(sub g)), non-pigmented particles (a(sub d)), and non-pigmented particles plus CDOM (a(sub dg)), and chlorophyll a concentration ([Chl_a]). Several algorithms were compared to derive constituent absorption coefficients from remote sensing reflectance (R(sub rs)) ratios. The validation match-ups showed that the mean absolute percent differences (MAPD) were typically less than 35%, although higher errors were found for a(sub d) retrievals. Seasonal and spatial variability of satellite-derived absorption coefficients and [Chl_a] was apparent and consistent with field data. CDOM is a major contributor to the bio-optical properties of the SMAB, accounting for 35-70% of total light absorption by particles plus CDOM at 443 nm, as compared to 30-45% for phytoplankton and 0-20% for non-pigmented particles. The overestimation of [Chl_a] from the operational satellite algorithms may be attributed to the strong CDOM absorption in this region. River discharge is important in controlling the bio-optical environment, but cannot explain all of the regional and seasonal variability of biogeochemical constituents in the SMAB.

Pan, Xiaoju↗
NASA NTRS2013

Ion Exchange Technology Development in Support of the Urine Processor Assembly

The urine processor assembly (UPA) on the International Space Station (ISS) recovers water from urine via a vacuum distillation process. The distillation occurs in a rotating distillation assembly (DA) where the urine is heated and subjected to sub-ambient pressure. As water is removed, the original organics, salts, and minerals in the urine become more concentrated and result in urine brine. Eventually, water removal will concentrate the urine brine to super saturation of individual constituents, and precipitation occurs. Under typical UPA DA operating conditions, calcium sulfate or gypsum is the first chemical to precipitate in substantial quantity. During preflight testing with ground urine, the UPA achieved 85% water recovery without precipitation. However, on ISS, it is possible that crewmember urine can be significantly more concentrated relative to urine from ground donors. As a result, gypsum precipitated in the DA when operating at water recovery rates at or near 85%, causing the failure and subsequent re14 NASA Tech Briefs, September 2013 placement of the DA. Later investigations have demonstrated that an excess of calcium and sulfate will cause precipitation at water recovery rates greater than 70%. The source of the excess calcium is likely physiological in nature, via crewmembers' bone loss, while the excess sulfate is primarily due to the sulfuric acid component of the urine pretreatment. To prevent gypsum precipitation in the UPA, the Precipitation Prevention Project (PPP) team has focused on removing the calcium ion from pretreated urine, using ion exchange resins as calcium removal agents. The selectivity and effectiveness of ion exchange resins are determined by such factors as the mobility of the liquid phase through the polymer matrix, the density of functional groups, type of functional groups bound to the matrix, and the chemical characteristics of the liquid phase (pH, oxidation potential, and ionic strength). Previous experience with ion exchange resins has demonstrated that the most effective implementation for an ion exchange resin is a cartridge, or column, in which the resin is contained. Based on the results of equilibrium and sub-scale dynamic column testing, a possible solution for mitigating the calcium precipitation issue on the ISS has been identified. From an original pool of 13 ion exchange resins, two candidates have been identified that demonstrate substantial calcium removal on the sub-scale. The dramatic reduction in resin performance from published calcium uptake demonstrates the need for thorough evaluation of resins at the low pH and strong oxidizing environment present in the UPA. Chemical variations in the influent (calcium concentrations and pretreatment dosing) appear to have a noticeable impact on the calcium capacity of the resin. Low calcium concentrations and high pretreatment dosing will likely result in a decrease in calcium capacity. Conversely, low pre trea t - ment dosing will likely result in an increase in calcium capacity. In contrast, investigations at a variety of flow rates, length-to-diameter ratios, resin volumes, and flow regimes (continuous versus pulsed) show that changes in physical parameters do not have substantial impacts on resin performance in the very low specific velocity ranges of interest. This result is particularly useful because most commercial applications at higher specific velocities do show a relatively strong relationship between flow and capacity. The lack of a strong relationship will allow more flexibility in the implementation of an ion exchange bed for flight. Verification of subscale tests with flight-scale resin beds is recommended prior to implementation in the on-orbit UPA.

Mitchell, Julie↗
NASA NTRS2001

TGF-beta1 release from biodegradable polymer microparticles: its effects on marrow stromal osteoblast function

BACKGROUND: Controlled release of transforming growth factor-beta1 (TGF-beta1) to a bone defect may be beneficial for the induction of a bone regeneration cascade. The objectives of this work were to assess the feasibility of using biodegradable polymer microparticles as carriers for controlled TGF-beta1 delivery and the effects of released TGF-beta1 on the proliferation and differentiation of marrow stromal cells in vitro. METHODS: Recombinant human TGF-beta1 was incorporated into microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG). Fluorescein isothiocynate-labeled bovine serum albumin (FITC-BSA) was co-encapsulated as a porogen. The effects of PEG content (0, 1, or 5% by weight [wt%]) and buffer pH (3, 5, or 7.4) on the protein release kinetics and the degradation of PLGA were determined in vitro for as long as 28 days. Rat marrow stromal cells were seeded on a biodegradable poly(propylene fumarate) (PPF) substrate. The dose response and biological activity of released TGF-beta1 was determined after 3 days in culture. The effects of TGF-beta1 released from PLGA/PEG microparticles on marrow stromal cell proliferation and osteoblastic differentiation were assessed during a 21-day period. RESULTS: TGF-beta1 was encapsulated along with FITC-BSA into PLGA/PEG blend microparticles and released in a multiphasic fashion including an initial burst for as long as 28 days in vitro. Increasing the initial PEG content resulted in a decreased cumulative mass of released proteins. Aggregation of FITC-BSA occurred at lower buffer pH, which led to decreased release rates of both proteins. The degradation of PLGA was increased at higher PEG content and significantly accelerated at acidic pH conditions. Rat marrow stromal cells cultured on PPF substrates showed a dose response to TGF-beta1 released from the microparticles similar to that of added TGF-beta1, indicating that the activity of TGF-beta1 was retained during microparticle fabrication and after growth factor release. At an optimal TGF-beta1 dosage of 1.0 ng/ml after 3 days, the released TGF-beta1 enhanced the proliferation and osteoblastic differentiation of marrow stromal cells over 21 days of culture, with increased total cell number, alkaline phosphatase activity, and osteocalcin production. CONCLUSIONS: PLGA/PEG blend microparticles can serve as delivery vehicles for controlled release of TGF-beta1, and the released growth factor enhances marrow stromal cell proliferation and osteoblastic differentiation in vitro. CLINICAL RELEVANCE: Controlled release of TGF-beta1 from PLGA/PEG microparticles is representative of emerging tissue engineering technologies that may modulate cellular responses to encourage bone regeneration at a skeletal defect site.

Non-NASA Center↗
NASA NTRS1987

The preservation of urine samples for determination of renal stone risk factors

A preservation technique for urine specimens before determination of stone risk factors was evaluated. The purpose of these experiments was to prove the effectiveness of the preservatives used to prevent changes in the concentrations of those constituents measured. Measured concentrations in fresh specimens were compared with those in the same specimens after storage with the preservatives. Refrigeration at 4 degrees C up to five days was appropriate in a laboratory setting, as no significant changes in urinary concentrations occurred. Refrigeration, however, did not offer a convenient method for shipping. Chemical preservation was found to be an effective alternative to refrigeration. Thymol prevented changes in concentration of pH, citrate, uric acid, sulfate, sodium, potassium, and cyclic AMP, while a mixture of hydrochloric (HCl) acid and boric acid prevented changes in calcium, magnesium, phosphorus, oxalate, ammonium, and creatinine. Thus, the addition of thymol or HCl/boric acid to urine specimens will prevent significant changes in the concentrations of stone risk factors.

Non-NASA Center↗
DOE OSTI2022

Synergistic effect of microstructure and defects on the initiation of fatigue cracks in additively manufactured Inconel 718

Fatigue cracks in additively manufactured (AMed) Inconel 718 (IN-718) in machined surface condition often initiate from persistent slip bands (PSBs) unlike other popular AM alloys such as 17-4 PH stainless steel or Ti-6Al-4V, where fatigue crack initiation is exclusively from volumetric defects; therefore, a competition between PSB- vs. defect- mediated crack initiation clearly exists. To shed light on the factors governing the competition, this study investigates the characteristics of cyclic strain localization, PSB formation, and crack initiation via crystal plasticity (CP) modeling of cyclic loading on polycrystalline aggregates which are then validated by experiments. In this work, a physics-based, free slip distance (FSD) dependent slip strength evolution law is proposed, which is shown to enable the CP model to simulate the heterogeneous strain distribution in IN-718. Implementing a crack initiation criterion based on strain contrast, the locations and lives for crack initiation can also be calculated. It is shown that both FSD and resolve shear stress influence the strain localization and crack initiation behaviors. The distribution of a localization parameter calculated based on the multiplication of FSD and Schmid factor within a grain is found to correlate well with the locations of PSBs. The maximum values of the localization parameters within a microstructure are shown to correlate well with the experimentally obtained crack initiation lives. The presence of volumetric defects in IN-718 generally do not impact strain localization behavior unless their size is large compared to the grain size.

42 ENGINEERING↗
DOE OSTI2020

Anaerobic respiration pathways and response to increased substrate availability of Arctic wetland soils

The availability of labile carbon (C) compounds in Arctic wetland soils is expected to increase due to thawing permafrost and increased fermentation as a result of decomposition of organic matter with warming. How microbial communities respond to this change will affect the balance of CO 2 and CH 4 emitted during anaerobic organic matter decomposition, and ultimately the net radiative forcing of greenhouse gas emissions from these soils. While soil water content limits aerobic respiration, the factors controlling methanogenesis and anaerobic respiration are poorly defined in suboxic Arctic soils. In this study, we conducted incubation experiments on two tundra soils from field sites on the Seward Peninsula, Alaska, with contrasting pH and geochemistry to determine the pathways of anaerobic microbial respiration and changes with increasing substrate availability upon warming. In incubation of soils from the circumneutral Teller site, the ratio of CO 2 to CH 4 dropped from 10 to <2 after 60 days, indicating rapid depletion of alternative terminal electron acceptors (TEAs). Addition of acetate stimulated production of CO 2 and CH 4 in a nearly 1:1 ratio, consistent with methanogenesis, and the composition of the microbial community shifted to favor clades capable of utilizing the added acetate such as the Fe(III)-reducing Geobacter and the methanogenic archaea Methanosarcina. In contrast, both CO 2 and CH 4 production declined with acetate addition during incubation of soils from the more acidic Council site, and fermentative microorganisms increased in abundance despite the high availability of fermentation products. These results demonstrate that the degree to which increasing substrate availability stimulates greenhouse gas production in tundra wetlands will vary widely depending on soil pH and geochemistry.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1993

Alterations in renal stone risk factors after space flight

Exposure to the microgravity environment of space produces a number of physiological changes of metabolic and environmental origin that could increase the potential for renal stone formation. Metabolic, environmental and physicochemical factors that influence renal stone risk potential were examined in 24-hour urine samples from astronauts 10 days before launch and on landing day to provide an immediate postflight assessment of these factors. In addition, comparisons were made between male and female crewmembers, and between crewmembers on missions of less than 6 days and those on 6 to 10-day missions. Results suggest that immediately after space flight the risk of calcium oxalate and uric acid stone formation is increased as a result of metabolic (hypercalciuria, hypocitraturia, pH) and environmental (lower urine volume) derangements, some of which could reflect residual effects of having been exposed to microgravity.

NASA Center JSC↗
DOE OSTI2014

Photochemical oxidation of dissolved elemental mercury by carbonate radicals in water

In this study, photochemical oxidation of dissolved elemental mercury, Hg(0), affects mercury chemical speciation and its transfer at the water-air interface in the aquatic environment. The mechanisms and factors that control Hg(0) photooxidation, however, are not completely understood, especially concerning the role of dissolved organic matter (DOM) and carbonate (CO 3 2- ) in natural freshwaters. Here, we evaluate Hg(0) photooxidation rates affected by reactive ionic species (e.g., DOM, CO 3 2- , and NO 3 – ) and free radicals in creek water and a phosphate buffer solution (pH 8) under simulated solar irradiation. The Hg(0) photooxidation rate (k = 1.44 h -1 ) is much higher in the presence of both CO 3 2- and NO 3 - than in the presence of CO 3 2- , NO 3 - , or DOM alone (k = 0.1–0.17 h -1 ). Using scavengers and enhancers for singlet oxygen ( 1 O 2 ) and hydroxyl (HO • ) radicals, as well as electron paramagnetic resonance spectroscopy, we found that carbonate radicals (CO 3 •- ) primarily drive Hg(0) photooxidation. The addition of DOM to the solution of CO 3 2- and NO 3 - decreased the oxidation rate by half. This study identifies an unrecognized pathway of Hg(0) photooxidation by CO 3 •- radicals and the inhibitory effect of DOM, which could be important in assessing Hg transformation and the fate of Hg in water containing carbonate such as hard water and seawater.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Evaluation of Potential Toxic Metals Accumulation in Wheat Irrigated with Wastewater

The present study was carried out to ascertain the level of various metals in wheat variety (Chagi–4) irrigated with diverse doses of wastewater. The concentration of metals in soil, water and wheat grain samples was examined through an atomic absorption spectrophotometer. In wheat grains, the mean values of metals (mg/kg) varied from 0.06 to 0.2 for Pb, 1.2 to 1.6 for Cd, 0.6 to 0.9 for Ni, 0.8 to 1.6 for Fe, 0.4 to 1.0 for Mn, 0.7 to 1.4 for Cu, 0.3 to 0.5 for Cr, 0.1 to 0.9 for Zn and 0.03 to 0.2 for Co, correspondingly. Measured concentrations were found within the permissible limit given by FAO/WHO except for cadmium whose concentration exceeded an acceptable limit 0.2 mg/kg suggested by FAO/WHO. It might be due to high soil pH, which hinders the efficient transfer of metals between different mediums. Wastewater irrigated soil, wheat and water had high metal values, but the low rate of transfer was noticed from soil to grains. Higher bioconcentration factor was obtained for manganese and cadmium; cadmium had even higher pollution load index, which could indicate the contamination status of soil. Therefore, regular monitoring of wastewater is necessary to prevent the excessive build-up of metals.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Impact of ionomer adsorption on alkaline hydrogen oxidation activity and fuel cell performance

The adsorption of the ionomer components significantly impacts the activity of hydrogen oxidation reaction (HOR) catalysts under high pH conditions. Two specific adsorptions, i.e., (i) cation-hydroxide-water co-adsorption and (ii) phenyl group adsorption, on the surface of platinum group metal HOR catalysts were identified as the performance-limiting factors for anion-exchange membrane fuel cells (AEMFCs). Here, we review the main characteristics of the surface adsorptions, their impact on the performance of HOR half-cell and AEMFC, and the mitigation strategies. This review emphasizes important aspects in the design of electrocatalysts and ionomers for improved AEMFC performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Perspective on Technical Lignin Fractionation

Technical lignin extracted from pulping and biorefining processes provides a class of complex and polydisperse phenolic polymers. Preparation of lignin with lower structural complexity and polydispersity through lignin fractionation is one of the primary solutions to engineer lignin into a value-added material. Sequential lignin fraction by pH controlled precipitation from 12 to 1 is one of the primary developed methods. Partial solubility of lignin in organic solvents is another promising method for lignin fractionation. Organic solvents with different polarity and solubility factors are able to fractionate lignin, yielding a more homogeneous chemical structure. As a modification of the lignin fractionation process using solvents, water/organic solvents mixture, such as propan-2-one, alcohols, and acetic acid, from room to high temperature has been proposed as a greener method for lignin fractionation. Using membrane technology is another promising method and current results indicate a good potential for lignin recovery and fractionation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1976

Streaming potential measurements of biosurfaces

A technique based on the measurement of streaming potentials has been developed to evaluate the electrokinetic region of the cell periphery. This approach is feasible for cell lines propagated in in-vitro cell cultures in monolayer form. The advantage of this system is that cells may be evaluated in the living state atttached to a substrate; it is not necessary to subject the cells to enzymatic, chemical, or mechanical trauma required to obtain monodisperse suspensions which are then normally evaluated by microelectrophoresis. In this manner, it should be possible to study the influence of substrate and environmental factors on the charge density and potential at the cell periphery. The apparatus and procedure are described as well as some results concerning the electrokinetic potential of borosilicate capillaries as a function of ionic strength, pH, and temperature. The effect that turbulence and entrance flow conditions have on accurate streaming-potential measurements is discussed. The electrokinetic potential of BALB/c 3T12 fibroblasts has been quantified as a function of pH, ionic strength, glutaraldehyde fixation, and Giemsa staining.

Van Wagenen, R. A.↗
DOE OSTI2014

Fabrication of FCC-SiO{sub 2} colloidal crystals using the vertical convective self-assemble method

In order to determine the optimal conditions for the growth of high-quality 250 nm-SiO{sub 2} colloidal crystals by the vertical convective self-assemble method, the Design of Experiments (DoE) methodology is applied. The influence of the evaporation temperature, the volume fraction, and the pH of the colloidal suspension is studied by means of an analysis of variance (ANOVA) in a 3{sup 3} factorial design. Characteristics of the stacking lattice of the resulting colloidal crystals are determined by scanning electron microscopy and angle-resolved transmittance spectroscopy. Quantitative results from the statistical test show that the temperature is the most critical factor influencing the quality of the colloidal crystal, obtaining highly ordered structures with FCC stacking lattice at a growth temperature of 40°C.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗