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Sample records for acid strong base

  1. Carbon-based strong solid acid for cornstarch hydrolysis

    NASA Astrophysics Data System (ADS)

    Nata, Iryanti Fatyasari; Irawan, Chairul; Mardina, Primata; Lee, Cheng-Kang

    2015-10-01

    Highly sulfonated carbonaceous spheres with diameter of 100-500 nm can be generated by hydrothermal carbonization of glucose in the presence of hydroxyethylsulfonic acid and acrylic acid at 180 °C for 4 h. The acidity of the prepared carbonaceous sphere C4-SO3H can reach 2.10 mmol/g. It was used as a solid acid catalyst for the hydrolysis of cornstarch. Total reducing sugar (TRS) concentration of 19.91 mg/mL could be obtained by hydrolyzing 20 mg/mL cornstarch at 150 °C for 6 h using C4-SO3H as solid acid catalyst. The solid acid catalyst demonstrated good stability that only 9% decrease in TRS concentration was observed after five repeat uses. The as-prepared carbon-based solid acid catalyst can be an environmentally benign replacement for homogeneous catalyst.

  2. Carbon-based strong solid acid for cornstarch hydrolysis

    SciTech Connect

    Nata, Iryanti Fatyasari; Irawan, Chairul; Mardina, Primata; Lee, Cheng-Kang

    2015-10-15

    Highly sulfonated carbonaceous spheres with diameter of 100–500 nm can be generated by hydrothermal carbonization of glucose in the presence of hydroxyethylsulfonic acid and acrylic acid at 180 °C for 4 h. The acidity of the prepared carbonaceous sphere C4-SO{sub 3}H can reach 2.10 mmol/g. It was used as a solid acid catalyst for the hydrolysis of cornstarch. Total reducing sugar (TRS) concentration of 19.91 mg/mL could be obtained by hydrolyzing 20 mg/mL cornstarch at 150 °C for 6 h using C4-SO{sub 3}H as solid acid catalyst. The solid acid catalyst demonstrated good stability that only 9% decrease in TRS concentration was observed after five repeat uses. The as-prepared carbon-based solid acid catalyst can be an environmentally benign replacement for homogeneous catalyst. - Highlights: • Carbon solid acid was successfully prepared by one-step hydrothermal carbonization. • The acrylic acid as monomer was effectively reduce the diameter size of particle. • The solid acid catalyst show good catalytic performance of starch hydrolysis. • The solid acid catalyst is not significantly deteriorated after repeated use.

  3. Clinical assessment of acid-base status. Strong ion difference theory.

    PubMed

    Constable, P D

    1999-11-01

    The traditional approach to evaluating acid-base balance uses the Henderson-Hasselbalch equation to categorize four primary acid-base disturbances: respiratory acidosis (increased PCO2), respiratory alkalosis (decreased PCO2), metabolic acidosis (decreased extracellular base excess), or metabolic alkalosis (increased extracellular base excess). The anion gap is calculated to detect the presence of unidentified anions in plasma. This approach works well clinically and is recommended for use whenever serum total protein, albumin, and phosphate concentrations are approximately normal; however, when their concentrations are markedly abnormal, the Henderson-Hasselbalch equation frequently provides erroneous conclusions as to the cause of an acid-base disturbance. Moreover, the Henderson-Hasselbalch approach is more descriptive than mechanistic. The new approach to evaluating acid-base balance uses the simplified strong ion model to categorize eight primary acid-base disturbances: respiratory acidosis (increased PCO2), respiratory alkalosis (decreased PCO2), strong ion acidosis (decreased [SID+]) or strong ion alkalosis (increased [SID+]), nonvolatile buffer ion acidosis (increased [ATOT]) or nonvolatile buffer ion alkalosis (decreased [ATOT]), and temperature acidosis (increased body temperature) or temperature alkalosis (decreased body temperature). The strong ion gap is calculated to detect the presence of unidentified anions in plasma. This simplified strong ion approach works well clinically and is recommended for use whenever serum total protein, albumin, and phosphate concentrations are markedly abnormal. The simplified strong ion approach is mechanistic and is therefore well suited for describing the cause of any acid-base disturbance. The new approach should therefore be valuable in a clinical setting and in research studies investigating acid-base balance. The presence of unmeasured strong ions in plasma or serum (such as lactate, ketoacids, and uremic anions

  4. A simplified strong ion model for acid-base equilibria: application to horse plasma.

    PubMed

    Constable, P D

    1997-07-01

    The Henderson-Hasselbalch equation and Stewart's strong ion model are currently used to describe mammalian acid-base equilibria. Anomalies exist when the Henderson-Hasselbalch equation is applied to plasma, whereas the strong ion model does not provide a practical method for determining the total plasma concentration of nonvolatile weak acids ([Atot]) and the effective dissociation constant for plasma weak acids (Ka). A simplified strong ion model, which was developed from the assumption that plasma ions act as strong ions, volatile buffer ions (HCO-3), or nonvolatile buffer ions, indicates that plasma pH is determined by five independent variables: PCO2, strong ion difference, concentration of individual nonvolatile plasma buffers (albumin, globulin, and phosphate), ionic strength, and temperature. The simplified strong ion model conveys on a fundamental level the mechanism for change in acid-base status, explains many of the anomalies when the Henderson-Hasselbalch equation is applied to plasma, is conceptually and algebraically simpler than Stewart's strong ion model, and provides a practical in vitro method for determining [Atot] and Ka of plasma. Application of the simplified strong ion model to CO2-tonometered horse plasma produced values for [Atot] (15.0 +/- 3.1 meq/l) and Ka (2.22 +/- 0.32 x 10(-7) eq/l) that were significantly different from the values commonly assumed for human plasma ([Atot] = 20.0 meq/l, Ka = 3.0 x 10(-7) eq/l). Moreover, application of the experimentally determined values for [Atot] and Ka to published data for the horse (known PCO2, strong ion difference, and plasma protein concentration) predicted plasma pH more accurately than the values for [Atot] and Ka commonly assumed for human plasma. Species-specific values for [Atot] and Ka should be experimentally determined when the simplified strong ion model (or strong ion model) is used to describe acid-base equilibria.

  5. Strong Relationships in Acid-Base Chemistry - Modeling Protons Based on Predictable Concentrations of Strong Ions, Total Weak Acid Concentrations, and pCO2.

    PubMed

    Ring, Troels; Kellum, John A

    2016-01-01

    Understanding acid-base regulation is often reduced to pigeonholing clinical states into categories of disorders based on arterial blood sampling. An earlier ambition to quantitatively explain disorders by measuring production and elimination of acid has not become standard clinical practice. Seeking back to classical physical chemistry we propose that in any compartment, the requirement of electroneutrality leads to a strong relationship between charged moieties. This relationship is derived in the form of a general equation stating charge balance, making it possible to calculate [H+] and pH based on all other charged moieties. Therefore, to validate this construct we investigated a large number of blood samples from intensive care patients, where both data and pathology is plentiful, by comparing the measured pH to the modeled pH. We were able to predict both the mean pattern and the individual fluctuation in pH based on all other measured charges with a correlation of approximately 90% in individual patient series. However, there was a shift in pH so that fitted pH in general is overestimated (95% confidence interval -0.072-0.210) and we examine some explanations for this shift. Having confirmed the relationship between charged species we then examine some of the classical and recent literature concerning the importance of charge balance. We conclude that focusing on the charges which are predictable such as strong ions and total concentrations of weak acids leads to new insights with important implications for medicine and physiology. Importantly this construct should pave the way for quantitative acid-base models looking into the underlying mechanisms of disorders rather than just classifying them. PMID:27631369

  6. Strong Relationships in Acid-Base Chemistry – Modeling Protons Based on Predictable Concentrations of Strong Ions, Total Weak Acid Concentrations, and pCO2

    PubMed Central

    Kellum, John A.

    2016-01-01

    Understanding acid-base regulation is often reduced to pigeonholing clinical states into categories of disorders based on arterial blood sampling. An earlier ambition to quantitatively explain disorders by measuring production and elimination of acid has not become standard clinical practice. Seeking back to classical physical chemistry we propose that in any compartment, the requirement of electroneutrality leads to a strong relationship between charged moieties. This relationship is derived in the form of a general equation stating charge balance, making it possible to calculate [H+] and pH based on all other charged moieties. Therefore, to validate this construct we investigated a large number of blood samples from intensive care patients, where both data and pathology is plentiful, by comparing the measured pH to the modeled pH. We were able to predict both the mean pattern and the individual fluctuation in pH based on all other measured charges with a correlation of approximately 90% in individual patient series. However, there was a shift in pH so that fitted pH in general is overestimated (95% confidence interval -0.072–0.210) and we examine some explanations for this shift. Having confirmed the relationship between charged species we then examine some of the classical and recent literature concerning the importance of charge balance. We conclude that focusing on the charges which are predictable such as strong ions and total concentrations of weak acids leads to new insights with important implications for medicine and physiology. Importantly this construct should pave the way for quantitative acid-base models looking into the underlying mechanisms of disorders rather than just classifying them. PMID:27631369

  7. Base excess or buffer base (strong ion difference) as measure of a non-respiratory acid-base disturbance.

    PubMed

    Siggaard-Andersen, O; Fogh-Andersen, N

    1995-01-01

    Stewart in 1983 (Can J Physiol Pharmacol 1983: 61: 1444) reintroduced plasma buffer base under the name "strong ion difference" (SID). Buffer base was originally introduced by Singer and Hastings in 1948 (Medicine (Baltimore) 1948: 27: 223). Plasma buffer base, which is practically equal to the sum of bicarbonate and albuminate anions, may be increased due to an excess of base or due to an increased albumin concentration. Singer and Hastings did not consider changes in albumin as acid-base disorders and therefore used the base excess, i.e., the actual buffer base minus the buffer base at normal pH and pCO2, as measure of a non-respiratory acid-base disturbance. Stewart and followers, however, consider changes in albumin concentration to be acid-base disturbances: a patient with normal pH, pCO2, and base excess but with increased plasma buffer base due to increased plasma albumin concentration get the diagnoses metabolic (strong ion) alkalosis (because plasma buffer base is increased) combined with metabolic hyperalbuminaemic acidosis. Extrapolating to whole blood, anaemia and polycytaemia should represent types of metabolic alkalosis and acidosis, respectively. This reveals that the Stewart approach is absurd and anachronistic in the sense that an increase or decrease in any anion is interpreted as indicating an excess or deficit of a specific acid. In other words, a return to the archaic definitions of acids and bases as being the same as anions and cations. We conclude that the acid-base status (the hydrogen ion status) of blood and extracellular fluid is described in terms of the arterial pH, the arterial pCO2, and the extracellular base excess. It is measured with a modern pH-blood gas analyser. The electrolyte status of the plasma is a description of the most important electrolytes, usually measured in venous blood with a dedicated electrolyte analyser, i.e., Na+, Cl-, HCO3-, and K+. Albumin anions contribute significantly to the anions, but calculation

  8. A molal-based model for strong acid chemistry at low temperatures (<200 to 298 K)

    NASA Astrophysics Data System (ADS)

    Marion, Giles M.

    2002-07-01

    Geochemical processes occurring in cold environments on Earth, Mars, and Europa have elicited considerable interest in the application of geochemical models to subzero temperatures. Few existing geochemical models explicitly include acid chemistry and those that do are largely restricted to temperatures ≥0°C or rely on the mole-fraction scale rather than the more common molal scale. This paper describes (1) use of the Clegg mole-fraction acid models to develop a molal-based model for hydrochloric, nitric, and sulfuric acids at low temperatures; (2) incorporation of acid chemistry and nitrate minerals into the FREZCHEM model; (3) validation and limitations of the derived acid model; and (4) simulation of hypothetical acidic brines for Europa. The Clegg mole-fraction acid models were used to estimate activities of water and mean ionic activity coefficients that serve as the database for estimating molal Pitzer-equation parameters for HCl (188 to 298 K), HNO 3 (228 to 298 K), and H 2SO 4 (208 to 298 K). Model eutectics for HNO 3 and H 2SO 4 agree with experimental measurements to within ± 0.2°C. In agreement with previous work, the experimental freezing point depression (fpd) data for pure HCl at subzero temperatures were judged to be flawed and unreliable. Three alternatives are discussed for handling HCl chemistry at subzero temperatures. In addition to defining the solubility of solid-phase acids, this work also adds three new nitrate minerals and six new acid salts to the FREZCHEM model and refines equilibria among water ice, liquid water, and water vapor over the temperature range from 180 to 298 K. The final system is parameterized for Na-K-Mg-Ca-H-Cl-SO 4-NO 3-OH-HCO 3-CO 3-CO 2-H 2O. Simulations of hypothetical MgSO 4-H 2SO 4-H 2O and Na 2SO 4-MgSO 4-H 2SO 4-H 2O brines for Europa demonstrate how freezing can convert a predominantly salt solution into a predominantly acid solution at subzero temperatures. This result has consequences for the effects of

  9. Acid-base assessment: when and how to apply the Henderson-Hasselbalch equation and strong ion difference theory.

    PubMed

    Constable, Peter D

    2014-07-01

    The Henderson-Hasselbalch equation is probably the most famous equation in biology but is more descriptive than mechanistic. The traditional approach to acid-base assessment using the Henderson-Hasselbalch equation provides a clinically useful and accurate method when plasma protein concentrations are within the reference range. The simplified strong ion approach is a mechanistic acid-base model that can provide new insight into complicated acid-base disturbances. The simplified strong ion approach should be used to evaluate acid-base balance whenever plasma protein concentrations are abnormal.

  10. Canadian Tire Money: An Analogy for Use When Discussing Weak Acid Strong Base Titrations

    NASA Astrophysics Data System (ADS)

    Last, Arthur M.

    2003-12-01

    A simple analogy can often provide an instructor with a means of helping students to understand an unfamiliar concept. An analogy involving money can be particularly helpful as most students have experience in dealing with a range of financial transactions in their everyday lives. In this article, use is made of the practice of one well-known Canadian retail chain in returning to its customers a small percentage of an item's purchase price in the form of imitation bank notes that can subsequently be spent in the chain's stores. An analogy is drawn between this practice and the determination of the pKa of a weak acid by titrating it with a strong base, taking into account the hydrolysis of the anion produced.

  11. Clinical assessment of acid-base status: comparison of the Henderson-Hasselbalch and strong ion approaches.

    PubMed

    Constable, Peter D.

    2000-01-01

    The traditional approach for clinically assessing acid-base status uses the Henderson-Hasselbalch equation to categorize 4 primary acid-base disturbances: respiratory acidosis (increased PCO2), respiratory alkalosis (decreased PCO2), metabolic acidosis (decreased extracellular base excess or actual HCO3- concentration), and metabolic alkalosis (increased extracellular base excess or actual HCO3- concentration). The anion gap is calculated to detect unidentified anions in plasma. This approach works well clinically and is recommended for use whenever serum total protein, albumin, and phosphate concentrations are approximately normal. However, because the Henderson-Hasselbalch approach is more descriptive than mechanistic, when these concentrations are markedly abnormal the Henderson-Hasselbalch equation frequently provides erroneous information as to the cause of an acid-base disturbance. The new quantitive physicochemical approach to evaluating acid-base balance uses the simplified strong ion model to categorize 6 primary acid-base disturbances: respiratory acidosis (increased PCO2), respiratory alkalosis (decreased PCO2), strong ion acidosis (decreased strong ion difference), strong ion alkalosis (increased strong ion difference), nonvolatile buffer ion acidosis (increased plasma concentrations of albumin, globulins, or phosphate), and nonvolatile buffer ion alkalosis (decreased plasma concentrations of albumin, globulins, or phosphate). The strong ion gap is calculated to detect unidentified anions in plasma. The simplified strong ion approach works well clinically and is recommended for use whenever serum total protein, albumin, or phosphate concentrations are markedly abnormal. The simplified strong ion approach is mechanistic and is therefore well suited for describing the cause of any acid-base disturbance.

  12. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    Protonation by carbonic acid H2CO3 of the strong base methylamine CH3NH2 in a neutral contact pair in aqueous solution is followed via Car-Parrinello molecular dynamics simulations. Proton transfer (PT) occurs to form an aqueous solvent-stabilized contact ion pair within 100 fs, a fast time scale associated with the compression of the acid-base hydrogen-bond (H-bond), a key reaction coordinate. This rapid barrierless PT is consistent with the carbonic acid-protonated base pKa difference that considerably favors the PT, and supports the view of intact carbonic acid as potentially important proton donor in assorted biological and environmental contexts. The charge redistribution within the H-bonded complex during PT supports a Mulliken picture of charge transfer from the nitrogen base to carbonic acid without altering the transferring hydrogen's charge from approximately midway between that of a hydrogen atom and that of a proton. PMID:26879554

  13. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    Protonation by carbonic acid H2CO3 of the strong base methylamine CH3NH2 in a neutral contact pair in aqueous solution is followed via Car-Parrinello molecular dynamics simulations. Proton transfer (PT) occurs to form an aqueous solvent-stabilized contact ion pair within 100 fs, a fast time scale associated with the compression of the acid-base hydrogen-bond (H-bond), a key reaction coordinate. This rapid barrierless PT is consistent with the carbonic acid-protonated base pKa difference that considerably favors the PT, and supports the view of intact carbonic acid as potentially important proton donor in assorted biological and environmental contexts. The charge redistribution within the H-bonded complex during PT supports a Mulliken picture of charge transfer from the nitrogen base to carbonic acid without altering the transferring hydrogen's charge from approximately midway between that of a hydrogen atom and that of a proton.

  14. A strategy for the preparation of thioantimonates based on the concept of weak acids and corresponding strong bases.

    PubMed

    Anderer, Carolin; Delwa de Alarcón, Natalie; Näther, Christian; Bensch, Wolfgang

    2014-12-15

    By following a new synthetic approach, which is based on the in situ formation of a basic medium by the reaction between the strong base Sb(V)S4 (3-) and the weak acid H2 O, it was possible to prepare three layered thioantimonate(III) compounds of composition [TM(2,2'-bipyridine)3 ][Sb6 S10 ] (TM=Ni, Fe) and [Ni(4,4'-dimethyl-2,2'-bipyridine)3 ][Sb6 S10 ] under hydrothermal conditions featuring two different thioantimonate(III) network topologies. The antimony source, Na3 SbS4 ⋅ 9 H2 O, undergoes several decomposition reactions and produces the Sb(III) S3 species, which condenses to generate the layered anion. The application of transition-metal complexes avoids crystallization of dense phases. The reactions are very fast compared to conventional hydrothermal/solvothermal syntheses and are much less sensitive to changes of the reaction parameters.

  15. Photoinduced strong acid-weak base reactions in a polar aprotic solvent

    NASA Astrophysics Data System (ADS)

    Lee, Young Min; Park, Sun-Young; Kim, Heesu; Gyum Kim, Taeg; Kwon, Oh-Hoon

    2016-06-01

    The excited-state proton transfer (ESPT) of the strong photoacid, N-methyl-7-hydroxyquinolinium, was studied in the presence of different weak bases such as methanol, ethanol, and dimethyl sulfoxide in an aprotic solvent of acetonitrile. Here, we present chemical kinetics analysis of the ESPT mechanism to explain biphasic fluorescence decay of the parent photoacid and the sign reversal of the rise and decay of the resulting conjugate-base fluorescence. The ESPT of the free photoacid showed a molecularity of 2 with reacting alcohol molecules. In the ground state, it was found that a fraction of the photoacid formed 1 : 2 hydrogen-bonded complexes with the residual water present in the aprotic solvent or 1 : 1 complexes with the additive alcohols. In the excited state, these adducts underwent proton transfer when complexed further with diffusing alcohol molecules.

  16. Hydrogen-bubble-propelled zinc-based microrockets in strongly acidic media.

    PubMed

    Gao, Wei; Uygun, Aysegul; Wang, Joseph

    2012-01-18

    Tubular polyaniline (PANI)/Zn microrockets are described that display effective autonomous motion in extreme acidic environments, without any additional chemical fuel. These acid-driven hydrogen-bubble-propelled microrockets have been electrosynthesized using the conical polycarbonate template. The effective propulsion in acidic media reflects the continuous thrust of hydrogen bubbles generated by the spontaneous redox reaction occurring at the inner Zn surface. The propulsion characteristics of PANI/Zn microrockets in different acids and in human serum are described. The observed speed-pH dependence holds promise for sensitive pH measurements in extreme acidic environments. The new microrockets display an ultrafast propulsion (as high as 100 body lengths/s) along with attractive capabilities including guided movement and directed cargo transport. Such acid-driven microtubular rockets offer considerable potential for diverse biomedical and industrial applications. PMID:22188367

  17. Strongly Acidic Auxin Indole-3-Methanesulfonic Acid

    PubMed Central

    Cohen, Jerry D.; Baldi, Bruce G.; Bialek, Krystyna

    1985-01-01

    A radiochemical synthesis is described for [14C]indole-3-methanesulfonic acid (IMS), a strongly acidic auxin analog. Techniques were developed for fractionation and purification of IMS using normal and reverse phase chromatography. In addition, the utility of both Fourier transform infrared spectrometry and fast atom bombardment mass spectrometry for analysis of IMS has been demonstrated. IMS was shown to be an active auxin, stimulating soybean hypocotyl elongation, bean first internode curvature, and ethylene production. IMS uptake by thin sections of soybean hypocotyl was essentially independent of solution pH and, when applied at a 100 micromolar concentration, IMS exhibited a basipetal polarity in its transport in both corn coleoptile and soybean hypocotyl sections. [14C]IMS should, therefore, be a useful compound to study fundamental processes related to the movement of auxins in plant tissues and organelles. PMID:16664007

  18. Formation of hydrogen-bonded chains between strong N-base and NH acids — a FTIR study

    NASA Astrophysics Data System (ADS)

    Brzezinski, Bogumil; Zundel, Georg

    1998-05-01

    Mixtures of imidazole derivatives with the strong base 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) were studied by FTIR spectroscopy as a function of the imidazole derivative:MTBD ratio. In the case of complexes of MTBD with the lowest acidic imidazole only molecular complexes are found. This is true in the chloroform solutions as well as in the acetonitrile solutions. With increasing acidity of the imidazoles in both solvents more and more polar structure of the complexes is found. In chloroform the polar structure predominates and the proton polarizability in the chains remains weak. In the acetonitrile solution the complexes dissociate. If more imidazole molecules are present one observes large proton polarizability of the negatively charged structurally symmetrical imidazole chains.

  19. Comparison of three strong ion models used for quantifying the acid-base status of human plasma with special emphasis on the plasma weak acids.

    PubMed

    Anstey, Chris M

    2005-06-01

    Currently, three strong ion models exist for the determination of plasma pH. Mathematically, they vary in their treatment of weak acids, and this study was designed to determine whether any significant differences exist in the simulated performance of these models. The models were subjected to a "metabolic" stress either in the form of variable strong ion difference and fixed weak acid effect, or vice versa, and compared over the range 25 < or = Pco(2) < or = 135 Torr. The predictive equations for each model were iteratively solved for pH at each Pco(2) step, and the results were plotted as a series of log(Pco(2))-pH titration curves. The results were analyzed for linearity by using ordinary least squares regression and for collinearity by using correlation. In every case, the results revealed a linear relationship between log(Pco(2)) and pH over the range 6.8 < or = pH < or = 7.8, and no significant difference between the curve predictions under metabolic stress. The curves were statistically collinear. Ultimately, their clinical utility will be determined both by acceptance of the strong ion framework for describing acid-base physiology and by the ease of measurement of the independent model parameters.

  20. The strong reactions of Lewis-base noble-metals with vanadium and other acidic transition metals

    SciTech Connect

    Ebbinghaus, B.B.

    1991-05-01

    The noble metals often thought of as unreactive solids,react strongly with nearly 40% of the elements in the periodictable: group IIIB-VB transition metals, lanthanides, theactinides, and group IIIA-IVA non-transition metals. These strong reactions arise from increased bonding/electron transfer fromnonbonding electrons d electron pairs on the noble metal tovacant orbitals on V, etc. This effect is a generalized Lewis acid-base interaction. The partial Gibbs energy of V in the noblemetals has been measured as a function of concentration at a temperature near 1000C. Thermodynamics of the intermetallics are determined by ternary oxide equilibria, ternary carbide equilibria, and the high-temperature galvanic cell technique. These experimental methods use equilibrated solid composite mixtures in which grains of V oxides or of V carbides are interspersed with grains of V-NM(noble-metal) alloys. In equilibrium the activity of V in the oxide or the carbide equals the activity in the alloy. Consequently, the thermodynamics available in the literature for the V oxides and V carbides are reviewed. Test runs on the galvanic cell were attempted. The V oxide electrode reacts with CaF[sub 2], ThO[sub 2], YDT(0.85ThO[sub 2]-0.15YO[sub 1.5]), and LDT(0.85ThO[sub 2]- 0.15LaO[sub 1.5]) to interfere with the measured data observed toward the beginning of a galvanic cell experiment are the most accurate. The interaction of vanadium at infinite dilution in the noble-metals was determined.

  1. The strong reactions of Lewis-base noble-metals with vanadium and other acidic transition metals

    SciTech Connect

    Ebbinghaus, B.B.

    1991-05-01

    The noble metals often thought of as unreactive solids,react strongly with nearly 40% of the elements in the periodictable: group IIIB-VB transition metals, lanthanides, theactinides, and group IIIA-IVA non-transition metals. These strong reactions arise from increased bonding/electron transfer fromnonbonding electrons d electron pairs on the noble metal tovacant orbitals on V, etc. This effect is a generalized Lewis acid-base interaction. The partial Gibbs energy of V in the noblemetals has been measured as a function of concentration at a temperature near 1000C. Thermodynamics of the intermetallics are determined by ternary oxide equilibria, ternary carbide equilibria, and the high-temperature galvanic cell technique. These experimental methods use equilibrated solid composite mixtures in which grains of V oxides or of V carbides are interspersed with grains of V-NM(noble-metal) alloys. In equilibrium the activity of V in the oxide or the carbide equals the activity in the alloy. Consequently, the thermodynamics available in the literature for the V oxides and V carbides are reviewed. Test runs on the galvanic cell were attempted. The V oxide electrode reacts with CaF{sub 2}, ThO{sub 2}, YDT(0.85ThO{sub 2}-0.15YO{sub 1.5}), and LDT(0.85ThO{sub 2}- 0.15LaO{sub 1.5}) to interfere with the measured data observed toward the beginning of a galvanic cell experiment are the most accurate. The interaction of vanadium at infinite dilution in the noble-metals was determined.

  2. Separation of oligonucleotides of identical size, but different base composition, by free zone capillary electrophoresis in strongly acidic, isoelectric buffers.

    PubMed

    Perego, M; Gelfi, C; Stoyanov, A V; Righetti, P G

    1997-12-01

    A novel method for analyzing oligonucleotides of the same length, but bearing a single base substitution, is reported, based on free zone capillary electrophoresis (CZE) under rather acidic pH values. For this purpose, a set of four 18-mers of fairly random base composition has been synthesized, bearing, in nucleotide 9, the following bases: T, C, G or A. Theoretical predictions, based on titration curves of single free nucleotides, allowed us to predict that the simultaneous separation of a mixture of all four oligonucleotides could be possible in a pH 3-4 window. In fact, electrophoresis at pH 5.7 gave a single, asymmetric peak, whereas CZE at pH 4.8 could resolve three out of four species (the T9 and G9 oligonucleotides co-migrating into a single zone). A unique separation power could be obtained at pH 3.3 in a buffer comprising an amphoteric species (isoelectric iminodiacetic acid, IDA) and 7 M urea. Although IDA exhibited a pI of 2.23 (for a 100 mM solution), the addition of 7 M urea (necessary to denature the oligonucleotides) raised the apparent pH of the solution to 3.3. PMID:9504830

  3. Rapid determination of the equivalence volume in potentiometric acid-base titrations to a preset pH-II Standardizing a solution of a strong base, graphic location of equivalence volume, determination of stability constants of acids and titration of a mixture of two weak acids.

    PubMed

    Ivaska, A

    1974-06-01

    A newly proposed method of titrating weak acids with strong bases is applied to standardize a solution of a strong base, to graphic determination of equivalence volume of acetic acid with an error of 0.2%, to calculate the stability constants of hydroxylammonium ion, boric acid and hydrogen ascorbate ion and to analyse a mixture of acetic acid and ammonium ion with an error of 0.2-0.7%.

  4. Theory of titration curves-VII The properties of derivative titration curves for strong acid-strong base and other isovalent ion-combination titrations.

    PubMed

    Meites, T; Meites, L

    1970-06-01

    This paper deals with isovalent ion-combination titrations based on reactions that can be represented by the equation M(n+) + X(n-) --> MX, where the activity of the product MX is invariant throughout a titration, and with the derivative titration curves obtained by plotting d[M(+)]/dfversus f for such titrations. It describes some of the ways in which such curves can be obtained; it compares and contrasts them both with potentiometric titration curves, which resemble them in shape, and with segmented titration curves, from which they are derived; and it discusses their properties in detail.

  5. Use of a quantitative strong ion approach to determine the mechanism for acid-base abnormalities in sick calves with or without diarrhea.

    PubMed

    Constable, Peter D; Stämpfli, Henry R; Navetat, Hérve; Berchtold, Joachim; Schelcher, François

    2005-01-01

    Acid-base abnormalities are frequently present in sick calves. The mechanism for an acid-base disturbance can be characterized using the strong ion approach, which requires accurate values for the total concentration of plasma nonvolatile buffers (A(tot)) and the effective dissociation constant for plasma weak acids (K(a)). The aims of this study were to experimentally determine A(tot), K(a), and net protein charge values for calf plasma and to apply these values quantitatively to data from sick calves to determine underlying mechanisms for the observed acid-base disturbance. Plasma was harvested from 9 healthy Holstein-Friesian calves and concentrations of quantitatively important strong ions (Na+, K+, Ca2+, Mg2+, Cl-, L-lactate) and nonvolatile buffer ions (total protein, albumin, phosphate) were determined. Plasma was tonometered with CO2 at 37 degrees C, and plasma P(CO2) and pH measured over a range of 15-159 mm Hg and 6.93-7.79, respectively. Strong ion difference (SID) was calculated from the measured strong ion concentrations, and nonlinear regression was used to estimate values for A(tot) and K(a) from the measured pH and P(CO2) and calculated SID. The estimated A(tot) and K(a) values were then validated using data from 2 in vivo studies. Mean (+/- SD) values for calf plasma were A(tot) = 0.343 mmol/g of total protein or 0.622 mmol/g of albumin; K(a) = (0.84 +/- 0.41) x 10(-7); pK(a) = 7.08. The net protein charge of calf plasma was 10.5 mEq/L, equivalent to 0.19 mEq/g of total protein or 0.34 mEq/g of albumin. Application of the strong ion approach to acid-base disturbances in 231 sick calves with or without diarrhea indicated that acidemia was due predominantly to a strong ion acidosis in response to hyponatremia accompanied by normochloremia or hyperchloremia and the presence of unidentified strong anions. These results confirm current recommendations that treatment of acidemia in sick calves with or without diarrhea should focus on intravenous or PO

  6. Evaluation of different approaches to quantify strong organic acidity and acid-base buffering of organic-rich surface waters in Sweden.

    PubMed

    Köhler, Stephan; Hruska, Jakub; Jönsson, Jörgen; Lövgren, Lars; Lofts, Stephen

    2002-11-01

    The role of organic acids in buffering pH in surface waters has been studied using a small brownwater stream (26mg L(-1) TOC) draining a forested catchment in Northern Sweden. Under the conditions of elevated pressure of CO2 stream field pH was changed between 3.5 and 6.1 during the acidification and alkalinization experiment. Acid-base characteristics of the natural organic matter were also determined using a high precision potentiometric method for a concentrated sample from the same stream. We compared the predictions from the Windermere Humic Aqueous Model (WHAM Model V), a model derived from the potentiometric titration (diprotic/monoprotic acid model) and a previously derived triprotic acid model which only uses alkalinity and TOC as input variables. The predicted buffering characteristics of all three models are very similar in the pH range 4.5-7 which suggests that during routine analysis alkalinity and TOC are sufficient to give a good estimate of organic acid anion charge contribution in a large range of surface waters. A slightly adjusted version of WHAM V successfully describes the organic charge contribution in a large number of sampled surface water lakes, which were previously used to calibrate the triprotic model.

  7. Mechanism of general acid-base catalysis in transesterification of an RNA model phosphodiester studied with strongly basic catalysts.

    PubMed

    Corona-Martínez, David O; Taran, Olga; Yatsimirsky, Anatoly K

    2010-02-21

    Using 80% vol aqueous DMSO as the reaction medium for transesterification of an RNA model substrate 2-hydroxypropyl 4-nitrophenyl phosphate allows one to observe catalysis in buffer mixtures composed of highly basic components such as guanidines, amidines or alkylamines, which provide up to 10(3)-fold accelerations over the background reaction in the 0.01-0.1 M concentration range. The rate law k(obs) = k(1)[B] + k(2)[B][BH(+)] was established indicating contributions from both simple general base catalysis and the reaction involving concerted action of neutral (B) and protonated (BH(+)) forms of the buffer. The catalytic efficiency of guanidinium and amidinium cations is 10 times larger than that of more acidic ammonium cations. Rate constants k(1) and k(2) obey the Brønsted equations with the slopes 0.77 and 0.69 respectively. Proton inventory for k(2) (B = guanidine) in D(2)O/H(2)O mixtures gives two fractionation factors phi(1) = 0.48 and phi(2) = 1.26 for normal and inverse isotope effects respectively. The former results from the proton transfer to B and the latter from the binding of guanidinium cation to the phosphate group as follows from observation of an inverse solvent isotope effect for the binding of guanidinium and amidinium cations to a phosphodiester anion. The results of kinetic studies together with analysis of transition state stabilization free energies for guanidinium and amidinium cations show that the protonated buffer component acts via electrostatic transition state stabilization rather than proton transfer, which may be possible for a guanidinium assisted hydroxide catalyzed reaction.

  8. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution II: Solvent Coordinate-Dependent Reaction Path.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    The protonation of methylamine base CH3NH2 by carbonic acid H2CO3 within a hydrogen (H)-bonded complex in aqueous solution was studied via Car-Parrinello dynamics in the preceding paper (Daschakraborty, S.; Kiefer, P. M.; Miller, Y.; Motro, Y.; Pines, D.; Pines, E.; Hynes, J. T. J. Phys. Chem. B 2016, DOI: 10.1021/acs.jpcb.5b12742). Here some important further details of the reaction path are presented, with specific emphasis on the water solvent's role. The overall reaction is barrierless and very rapid, on an ∼100 fs time scale, with the proton transfer (PT) event itself being very sudden (<10 fs). This transfer is preceded by the acid-base H-bond's compression, while the water solvent changes little until the actual PT occurrence; this results from the very strong driving force for the reaction, as indicated by the very favorable acid-protonated base ΔpKa difference. Further solvent rearrangement follows immediately the sudden PT's production of an incipient contact ion pair, stabilizing it by establishment of equilibrium solvation. The solvent water's short time scale ∼120 fs response to the incipient ion pair formation is primarily associated with librational modes and H-bond compression of water molecules around the carboxylate anion and the protonated base. This is consistent with this stabilization involving significant increase in H-bonding of hydration shell waters to the negatively charged carboxylate group oxygens' (especially the former H2CO3 donor oxygen) and the nitrogen of the positively charged protonated base's NH3(+). PMID:26876428

  9. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution II: Solvent Coordinate-Dependent Reaction Path.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    The protonation of methylamine base CH3NH2 by carbonic acid H2CO3 within a hydrogen (H)-bonded complex in aqueous solution was studied via Car-Parrinello dynamics in the preceding paper (Daschakraborty, S.; Kiefer, P. M.; Miller, Y.; Motro, Y.; Pines, D.; Pines, E.; Hynes, J. T. J. Phys. Chem. B 2016, DOI: 10.1021/acs.jpcb.5b12742). Here some important further details of the reaction path are presented, with specific emphasis on the water solvent's role. The overall reaction is barrierless and very rapid, on an ∼100 fs time scale, with the proton transfer (PT) event itself being very sudden (<10 fs). This transfer is preceded by the acid-base H-bond's compression, while the water solvent changes little until the actual PT occurrence; this results from the very strong driving force for the reaction, as indicated by the very favorable acid-protonated base ΔpKa difference. Further solvent rearrangement follows immediately the sudden PT's production of an incipient contact ion pair, stabilizing it by establishment of equilibrium solvation. The solvent water's short time scale ∼120 fs response to the incipient ion pair formation is primarily associated with librational modes and H-bond compression of water molecules around the carboxylate anion and the protonated base. This is consistent with this stabilization involving significant increase in H-bonding of hydration shell waters to the negatively charged carboxylate group oxygens' (especially the former H2CO3 donor oxygen) and the nitrogen of the positively charged protonated base's NH3(+).

  10. Reference electrode for strong oxidizing acid solutions

    DOEpatents

    Rigdon, Lester P.; Harrar, Jackson E.; Bullock, Sr., Jack C.; McGuire, Raymond R.

    1990-01-01

    A reference electrode for the measurement of the oxidation-reduction potentials of solutions is especially suitable for oxidizing solutions such as highly concentrated and fuming nitric acids, the solutions of nitrogen oxides, N.sub.2 O.sub.4 and N.sub.2 O.sub.5, in nitric acids. The reference electrode is fabricated of entirely inert materials, has a half cell of Pt/Ce(IV)/Ce(III)/70 wt. % HNO.sub.3, and includes a double-junction design with an intermediate solution of 70 wt. % HNO.sub.3. The liquid junctions are made from Corning No. 7930 glass for low resistance and negligible solution leakage.

  11. Understanding Acid Base Disorders.

    PubMed

    Gomez, Hernando; Kellum, John A

    2015-10-01

    The concentration of hydrogen ions is regulated in biologic solutions. There are currently 3 recognized approaches to assess changes in acid base status. First is the traditional Henderson-Hasselbalch approach, also called the physiologic approach, which uses the relationship between HCO3(-) and Pco2; the second is the standard base excess approach based on the Van Slyke equation. The third approach is the quantitative or Stewart approach, which uses the strong ion difference and the total weak acids. This article explores the origins of the current concepts framing the existing methods to analyze acid base balance.

  12. Acidity of Strong Acids in Water and Dimethyl Sulfoxide.

    PubMed

    Trummal, Aleksander; Lipping, Lauri; Kaljurand, Ivari; Koppel, Ilmar A; Leito, Ivo

    2016-05-26

    Careful analysis and comparison of the available acidity data of HCl, HBr, HI, HClO4, and CF3SO3H in water, dimethyl sulfoxide (DMSO), and gas-phase has been carried out. The data include experimental and computational pKa and gas-phase acidity data from the literature, as well as high-level computations using different approaches (including the W1 theory) carried out in this work. As a result of the analysis, for every acid in every medium, a recommended acidity value is presented. In some cases, the currently accepted pKa values were revised by more than 10 orders of magnitude. PMID:27115918

  13. Alloy B-10, a new nickel-based alloy for strong chloride-containing, highly acidic and oxygen-deficient environments

    SciTech Connect

    Kohler, M.; Kirchheiner, R.; Stenner, F.

    1998-12-31

    Alloy B-10 is a Ni-Mo-Cr alloy, recently developed for highly acidic but oxygen-deficient environments in the chemical process and environmental protection industries. The new nickel-based alloy with nominally (wt. %) 62 Ni, 24 MO, 8 Cr and 6 Fe, exhibits excellent corrosion resistance in intermediate concentrations of sulfuric acid, as well as in hydrochloric acid, even with additions of small amounts of oxidizing agents. In a simulated Flue Gas Desulfurization (FGD) environment of sulfuric acid of pH 1 with additions of 7% chloride and 0.01% fluoride, and also containing 15% gypsum the new alloy demonstrated high crevice corrosion resistance at 100 C, whereas a common Ni-Cr-Mo alloy of the C-type suffers crevice corrosion under the same conditions. This new alloy can easily be welded without filler or using matching filler. Good practical experience has been gained with Alloy B-10 in a district heating power station as a tube sheet and bottom wall liner for a glass tube heat exchanger working at 130 C with condensing 70% sulfuric acid.

  14. Solid extractant on the base of bifunctional extractants and solvating diluents for recovery of rare-earth and actinide elements from strongly acidic media

    SciTech Connect

    Romanovskii, V.N.; Smirnov, I.V.

    1996-12-31

    Diphosphine dioxides of different structure were synthesized and studied with the goal of using as a base for preparation of solid extractants. Of all the studied compounds, DPDO-11 was chosen. The solid extractant on its base was prepared by impregnation of divinylbenzene - styrol matrix with the solution of 0.8 M DPDO in fluoropol-1083. The investigation of extraction and physico-chemical properties of this solid extractant shows that it can be used for selective recovery of actinide and rare-earth elements from aqueous solutions in the wide range of acidity.

  15. Comparative study on sample stacking by moving reaction boundary formed with weak acid and weak or strong base in capillary electrophoresis: II. Experiments.

    PubMed

    Zhang, Wei; Fan, Liuyin; Shao, Jing; Li, Si; Li, Shan; Cao, Chengxi

    2011-04-15

    To demonstrate the theoretic method on the stacking of zwitterion with moving reaction boundary (MRB) in the accompanying paper, the relevant experiments were performed. The experimental results quantitatively show that (1) MRB velocity, including the comparisons between MRB and zwitterionic velocities, possesses key importance to the design of MRB stacking; (2) a much long front alkaline plug without sample should be injected before the sample injection for a complete stacking of zwitterion if sample buffer is prepared with strong base, conversely no such plug is needed if using a weak base as the sample buffer with proper concentration and pH value; (3) the presence of salt in MRB system holds dramatic effect on the MRB stacking if sample solution is a strong base, but has no effect if a weak alkali is used as sample solution; (4) all of the experiments of this paper, including the previous work, quantitatively manifest the theory and predictions shown in the accompanying paper. In addition, the so-called derivative MRB-induced re-stacking and transient FASI-induced re-stacking were also observed during the experiments, and the relevant mechanisms were briefly demonstrated with the results. The theory and its calculation procedures developed in the accompanying paper can be well used for the predictions to the MRB stacking of zwitterion in CE.

  16. Titration of strong and weak acids by sequential injection analysis technique.

    PubMed

    Maskula, S; Nyman, J; Ivaska, A

    2000-05-31

    A sequential injection analysis (SIA) titration method has been developed for acid-base titrations. Strong and weak acids in different concentration ranges have been titrated with a strong base. The method is based on sequential aspiration of an acidic sample zone and only one zone of the base into a carrier stream of distilled water. On their way to the detector, the sample and the reagent zones are partially mixed due to the dispersion and thereby the base is partially neutralised by the acid. The base zone contains the indicator. An LED-spectrophotometer is used as detector. It senses the colour of the unneutralised base and the signal is recorded as a typical SIA peak. The peak area of the unreacted base was found to be proportional to the logarithm of the acid concentration. Calibration curves with good linearity were obtained for a strong acid in the concentration ranges of 10(-4)-10(-2) and 0.1-3 M. Automatic sample dilution was implemented when sulphuric acid at concentration of 6-13 M was titrated. For a weak acid, i.e. acetic acid, a linear calibration curve was obtained in the range of 3x10(-4)-8x10(-2) M. By changing the volumes of the injected sample and the reagent, different acids as well as different concentration ranges of the acids can be titrated without any other adjustments in the SIA manifold or the titration protocol. PMID:18967966

  17. Titration of strong and weak acids by sequential injection analysis technique.

    PubMed

    Maskula, S; Nyman, J; Ivaska, A

    2000-05-31

    A sequential injection analysis (SIA) titration method has been developed for acid-base titrations. Strong and weak acids in different concentration ranges have been titrated with a strong base. The method is based on sequential aspiration of an acidic sample zone and only one zone of the base into a carrier stream of distilled water. On their way to the detector, the sample and the reagent zones are partially mixed due to the dispersion and thereby the base is partially neutralised by the acid. The base zone contains the indicator. An LED-spectrophotometer is used as detector. It senses the colour of the unneutralised base and the signal is recorded as a typical SIA peak. The peak area of the unreacted base was found to be proportional to the logarithm of the acid concentration. Calibration curves with good linearity were obtained for a strong acid in the concentration ranges of 10(-4)-10(-2) and 0.1-3 M. Automatic sample dilution was implemented when sulphuric acid at concentration of 6-13 M was titrated. For a weak acid, i.e. acetic acid, a linear calibration curve was obtained in the range of 3x10(-4)-8x10(-2) M. By changing the volumes of the injected sample and the reagent, different acids as well as different concentration ranges of the acids can be titrated without any other adjustments in the SIA manifold or the titration protocol.

  18. Acid rain effects on aluminum mobilization clarified by inclusion of strong organic acids.

    PubMed

    Lawrence, G B; Sutherland, J W; Boylen, C W; Nierzwicki-Bauer, S W; Momen, B; Baldigo, B P; Simonin, H A

    2007-01-01

    Assessments of acidic deposition effects on aquatic ecosystems have often been hindered by complications from naturally occurring organic acidity. Measurements of pH and ANCG, the most commonly used indicators of chemical effects, can be substantially influenced by the presence of organic acids. Relationships between pH and inorganic Al, which is toxic to many forms of aquatic biota, are also altered by organic acids. However, when inorganic Al concentrations are plotted against ANC (the sum of Ca2+, Mg2+, Na+, and K+, minus S042-, N03-, and Cl-), a distinct threshold for Al mobilization becomes apparent. If the concentration of strong organic anions is included as a negative component of ANC, the threshold occurs at an ANC value of approximately zero, the value expected from theoretical charge balance constraints. This adjusted ANC is termed the base-cation surplus. The threshold relationship between the base-cation surplus and Al was shown with data from approximately 200 streams in the Adirondack region of New York, during periods with low and high dissolved organic carbon concentrations, and for an additional stream from the Catskill region of New York. These results indicate that (1) strong organic anions can contribute to the mobilization of inorganic Al in combination with SO42- and N03-, and (2) the presence of inorganic Al in surface waters is an unambiguous indication of acidic deposition effects.

  19. Acid rain effects on aluminum mobilization clarified by inclusion of strong organic acids

    USGS Publications Warehouse

    Lawrence, G.B.; Sutherland, J.W.; Boylen, C.W.; Nierzwicki-Bauer, S. W.; Momen, B.; Baldigo, Barry P.; Simonin, H.A.

    2007-01-01

    Assessments of acidic deposition effects on aquatic ecosystems have often been hindered by complications from naturally occurring organic acidity. Measurements of pH and ANCG, the most commonly used indicators of chemical effects, can be substantially influenced by the presence of organic acids. Relationships between pH and inorganic Al, which is toxic to many forms of aquatic biota, are also altered by organic acids. However, when inorganic Al concentrations are plotted against ANC (the sum of Ca2+, Mg 2+, Na+, and K+, minus SO42-, NO3-, and Cl-), a distinct threshold for Al mobilization becomes apparent. If the concentration of strong organic anions is included as a negative component of ANC, the threshold occurs at an ANC value of approximately zero, the value expected from theoretical charge balance constraints. This adjusted ANC is termed the base-cation surplus. The threshold relationship between the base-cation surplus and Al was shown with data from approximately 200 streams in the Adirondack region of New York, during periods with low and high dissolved organic carbon concentrations, and for an additional stream from the Catskill region of New York. These results indicate that (1) strong organic anions can contribute to the mobilization of inorganic Al in combination with SO42- and NO 3-, and (2) the presence of inorganic Al in surface waters is an unambiguous indication of acidic deposition effects. ?? 2007 American Chemical Society.

  20. Acid rain effects on aluminum mobilization clarified by inclusion of strong organic acids.

    PubMed

    Lawrence, G B; Sutherland, J W; Boylen, C W; Nierzwicki-Bauer, S W; Momen, B; Baldigo, B P; Simonin, H A

    2007-01-01

    Assessments of acidic deposition effects on aquatic ecosystems have often been hindered by complications from naturally occurring organic acidity. Measurements of pH and ANCG, the most commonly used indicators of chemical effects, can be substantially influenced by the presence of organic acids. Relationships between pH and inorganic Al, which is toxic to many forms of aquatic biota, are also altered by organic acids. However, when inorganic Al concentrations are plotted against ANC (the sum of Ca2+, Mg2+, Na+, and K+, minus S042-, N03-, and Cl-), a distinct threshold for Al mobilization becomes apparent. If the concentration of strong organic anions is included as a negative component of ANC, the threshold occurs at an ANC value of approximately zero, the value expected from theoretical charge balance constraints. This adjusted ANC is termed the base-cation surplus. The threshold relationship between the base-cation surplus and Al was shown with data from approximately 200 streams in the Adirondack region of New York, during periods with low and high dissolved organic carbon concentrations, and for an additional stream from the Catskill region of New York. These results indicate that (1) strong organic anions can contribute to the mobilization of inorganic Al in combination with SO42- and N03-, and (2) the presence of inorganic Al in surface waters is an unambiguous indication of acidic deposition effects. PMID:17265932

  1. Analysis of aqueous solutions by near-infrared spectrometry (NIRS) II. Titrations of weak and very weak acids with strong bases

    NASA Astrophysics Data System (ADS)

    Molt, K.; Niemöller, A.; Cho, Y. J.

    1997-06-01

    The titrations of acetic and phosphoric acid with NaOH were observed by NIR-spectrometry. The measured spectra can be evaluated quantitatively for calibration of the H +-and OH --concentration. The NIRS errors with respect to the prediction of the pH and the equivalence point are discussed.

  2. Big, strong, neutral, twisted, and chiral π acids.

    PubMed

    Zhao, Yingjie; Huang, Guangxi; Besnard, Celine; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2015-04-13

    General synthetic access to expanded π-acidic surfaces of variable size, topology, chirality, and π acidity is reported. The availability of π surfaces with these characteristics is essential to develop the functional relevance of anion-π interactions with regard to molecular recognition, translocation, and transformation. The problem is that, with expanded π surfaces, the impact of electron-withdrawing substituents decreases and the high π acidity needed for strong anion-π interactions can be more difficult to obtain. To overcome this problem, it is herein proposed to build large surfaces from smaller fragments and connect these fragments with bridges that are composed only of single atoms. Two central surfaces for powerful anion-π interactions, namely, perfluoroarenes and naphthalenediimides (NDIs), were selected as fragments and coupled with through sulfide bridges. Their oxidation to sulfoxides and sulfones, as well as fluorine substitution in the peripheral rings, provides access to the full chemical space of relevant π acidities. According to cyclic voltammetry, LUMO levels range from -3.96 to -4.72 eV. With sulfoxide bridges, stereogenic centers are introduced to further enrich the intrinsic planar chirality of the expanded surfaces. The stereoisomers were separated by chiral HPLC and characterized by X-ray crystallography. Their topologies range from chairs to π boats, and the latter are reminiscent of the cation-π boxes in operational neuronal receptors. With pentafluorophenyl acceptors, the π acidity of NDIs with two sulfoxide groups in the core reaches -4.45 eV, whereas two sulfone moieties give a value of -4.72 eV, which is as low as with four ethyl sulfone groups, that is, a π superacid near the limit of existence. Beyond anion-π interactions, these conceptually innovative π-acidic surfaces are also of interest as electron transporters in conductive materials.

  3. Computer-assisted Gran titration procedure for strong acid determination

    SciTech Connect

    Phillips, M.F.; Gaffney, J.S.; Goodrich, R.W.; Tanner, R.L.

    1984-10-01

    An automated method for determining, by coulometric titration, small amounts of strong acid in the presence of weak acids is given. Essentially, a pH meter and a coulometer are coupled with a Tektronix 4052 mini-computer, and a two-step computer program then directs the titration and calculates the equivalence point by the method of Gran. A comparison of precision and accuracy of results for test solutions by manual and automated data reduction methods is presented. The method is being used successfully to analyze for the H/sup +/ content in ambient aerosol samples from aerometric field experiments, and can be used for cloud and rainwater samples as well. 3 references, 1 figure, 1 table.

  4. Upconversion nanoparticles with a strong acid-resistant capping

    NASA Astrophysics Data System (ADS)

    Recalde, Ileana; Estebanez, Nestor; Francés-Soriano, Laura; Liras, Marta; González-Béjar, María; Pérez-Prieto, Julia

    2016-03-01

    Water-dispersible upconversion nanoparticles (β-NaYF4:Yb3+,Er3+, UCNP) coated with a thin shell of a biocompatible copolymer comprising 2-hydroxyethylmethacrylate (HEMA) and 2-acrylamido-2-methyl-1-propanesulphonsulphonic acid (AMPS), which we will term COP, have been prepared by multidentate grafting. This capping is remarkably resistant to strong acidic conditions as low as pH 2. The additional functionality of the smart UCNP@COP nanosystem has been proved by its association to a well-known photosensitizer (namely, methylene blue, MB). The green-to-red emission ratio of the UC@COP@MB nanohybrid exhibits excellent linear dependence in the 7 to 2 pH range as a consequence of the release of the dye as the pH decreases.Water-dispersible upconversion nanoparticles (β-NaYF4:Yb3+,Er3+, UCNP) coated with a thin shell of a biocompatible copolymer comprising 2-hydroxyethylmethacrylate (HEMA) and 2-acrylamido-2-methyl-1-propanesulphonsulphonic acid (AMPS), which we will term COP, have been prepared by multidentate grafting. This capping is remarkably resistant to strong acidic conditions as low as pH 2. The additional functionality of the smart UCNP@COP nanosystem has been proved by its association to a well-known photosensitizer (namely, methylene blue, MB). The green-to-red emission ratio of the UC@COP@MB nanohybrid exhibits excellent linear dependence in the 7 to 2 pH range as a consequence of the release of the dye as the pH decreases. Electronic supplementary information (ESI) available: Additional spectra and data of HEMA, AMPS, COP, UCNP@oleate, UCNP@COP, and UCNP@COP@MB. See DOI: 10.1039/c5nr06653k

  5. General synthesis of 2,1-benzisoxazoles (anthranils) from nitroarenes and benzylic C-H acids in aprotic media promoted by combination of strong bases and silylating agents.

    PubMed

    Wiȩcław, Michał; Bobin, Mariusz; Kwast, Andrzej; Bujok, Robert; Wróbel, Zbigniew; Wojciechowski, Krzysztof

    2015-11-01

    Carbanions of phenylacetonitriles, benzyl sulfones, and dialkyl benzylphosphonates add nitroarenes at the ortho-position to the nitro group to form [Formula: see text]-adducts that, upon treatment with trialkylchlorosilane and additional base (t-BuOK or DBU), transform into 3-aryl-2,1-benzisoxazoles in moderate-to-good yields.

  6. The Acid-Base Titration of a Very Weak Acid: Boric Acid

    ERIC Educational Resources Information Center

    Celeste, M.; Azevedo, C.; Cavaleiro, Ana M. V.

    2012-01-01

    A laboratory experiment based on the titration of boric acid with strong base in the presence of d-mannitol is described. Boric acid is a very weak acid and direct titration with NaOH is not possible. An auxiliary reagent that contributes to the release of protons in a known stoichiometry facilitates the acid-base titration. Students obtain the…

  7. Dehydration polycondensation of dicarboxylic acids and diols using sublimating strong brønsted acids.

    PubMed

    Moyori, Takaya; Tang, Tang; Takasu, Akinori

    2012-05-14

    We investigated catalytic activities of strong brønsted acids for dehydration polycondensations of dicarboxylic acids and diols, which were carried out at low temperature (<100 °C) under reduced pressure (0.3-3 mmHg). Strong Brønsted acids, bis(perfluoroalkanesulfonyl)imide and perfluoroalkanesulfonic acid, showed higher activity than p-toluenesulfonic acid or rare-earth catalysts at 60 °C. In particular, bis(nonafluorobutanesulfonyl)imide (Nf(2)NH) showed the highest activity to synthesize not only aliphatic polyester (M(n) > 19000) but also aromatic polyester (M(n) > 7000). The used Nf(2)NH was sublimated from the reaction flask during polycondensation, and the sublimate, Nf(2)NH, was extra pure so that we can reuse the catalyst without loss of the activity in the dehydration polycondensations.

  8. Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 1. Minor structures

    USGS Publications Warehouse

    Leenheer, J.A.; Wershaw, R. L.; Reddy, M.M.

    1995-01-01

    An investigation of the strong-acid characteristics (pKa 3.0 or less) of fulvic acid from the Suwannee River, Georgia, was conducted. Quantitative determinations were made for amino acid and sulfur-containing acid structures, oxalate half-ester structures, malonic acid structures, keto acid structures, and aromatic carboxyl-group structures. These determinations were made by using a variety of spectrometric (13C-nuclear magnetic resonance, infrared, and ultraviolet spectrometry) and titrimetric characterizations on fulvic acid or fulvic acid samples that were chemically derivatized to indicate certain functional groups. Only keto acid and aromatic carboxyl-group structures contributed significantly to the strong-acid characteristics of the fulvic acid; these structures accounted for 43% of the strong-acid acidity. The remaining 57% of the strong acids are aliphatic carboxyl groups in unusual and/or complex configurations for which limited model compound data are available.

  9. Strong Motion Seismograph Based On MEMS Accelerometer

    NASA Astrophysics Data System (ADS)

    Teng, Y.; Hu, X.

    2013-12-01

    The MEMS strong motion seismograph we developed used the modularization method to design its software and hardware.It can fit various needs in different application situation.The hardware of the instrument is composed of a MEMS accelerometer,a control processor system,a data-storage system,a wired real-time data transmission system by IP network,a wireless data transmission module by 3G broadband,a GPS calibration module and power supply system with a large-volumn lithium battery in it. Among it,the seismograph's sensor adopted a three-axis with 14-bit high resolution and digital output MEMS accelerometer.Its noise level just reach about 99μg/√Hz and ×2g to ×8g dynamically selectable full-scale.Its output data rates from 1.56Hz to 800Hz. Its maximum current consumption is merely 165μA,and the device is so small that it is available in a 3mm×3mm×1mm QFN package. Furthermore,there is access to both low pass filtered data as well as high pass filtered data,which minimizes the data analysis required for earthquake signal detection. So,the data post-processing can be simplified. Controlling process system adopts a 32-bit low power consumption embedded ARM9 processor-S3C2440 and is based on the Linux operation system.The processor's operating clock at 400MHz.The controlling system's main memory is a 64MB SDRAM with a 256MB flash-memory.Besides,an external high-capacity SD card data memory can be easily added.So the system can meet the requirements for data acquisition,data processing,data transmission,data storage,and so on. Both wired and wireless network can satisfy remote real-time monitoring, data transmission,system maintenance,status monitoring or updating software.Linux was embedded and multi-layer designed conception was used.The code, including sensor hardware driver,the data acquisition,earthquake setting out and so on,was written on medium layer.The hardware driver consist of IIC-Bus interface driver, IO driver and asynchronous notification driver. The

  10. MOF-Derived Tungstated Zirconia as Strong Solid Acids toward High Catalytic Performance for Acetalization.

    PubMed

    Wang, Peng; Feng, Jian; Zhao, Yupei; Wang, Shaobin; Liu, Jian

    2016-09-14

    A strong solid acid, tungstated zirconia (WZ), has been prepared first using tungstate immobilized UiO-66 as precursors through a "double-solvent" impregnation method under mild calcination temperature. With moderate W contents, the as-synthesized WZ catalysts possess a high density of acid sites, and the proper heat treatment also has facilely led to a bunch of oligomeric tungsten clusters on stabilized tetragonal ZrO2. The resultant solid acids show an improved catalytic performance toward the benzaldehyde's acetalization in comparison with traditional zirconium hydroxide-prepared WZ. Notably, due to large surface area and additionally introduced strong acid sites, the MOF-derived WZ catalysts afforded conversion up to 86.0%. The facile method endows the WZ catalysts with superior catalytic activities and excellent recyclability, thus opening a new avenue for preparation of metal oxide-based solid superacids and superbases. PMID:27557351

  11. Acid-Base Homeostasis.

    PubMed

    Hamm, L Lee; Nakhoul, Nazih; Hering-Smith, Kathleen S

    2015-12-01

    Acid-base homeostasis and pH regulation are critical for both normal physiology and cell metabolism and function. The importance of this regulation is evidenced by a variety of physiologic derangements that occur when plasma pH is either high or low. The kidneys have the predominant role in regulating the systemic bicarbonate concentration and hence, the metabolic component of acid-base balance. This function of the kidneys has two components: reabsorption of virtually all of the filtered HCO3(-) and production of new bicarbonate to replace that consumed by normal or pathologic acids. This production or generation of new HCO3(-) is done by net acid excretion. Under normal conditions, approximately one-third to one-half of net acid excretion by the kidneys is in the form of titratable acid. The other one-half to two-thirds is the excretion of ammonium. The capacity to excrete ammonium under conditions of acid loads is quantitatively much greater than the capacity to increase titratable acid. Multiple, often redundant pathways and processes exist to regulate these renal functions. Derangements in acid-base homeostasis, however, are common in clinical medicine and can often be related to the systems involved in acid-base transport in the kidneys.

  12. Complexes of carborane acids linked by strong hydrogen bonds: acidity scales.

    PubMed

    Grabowski, Sławomir J

    2016-06-28

    Carborane acids, currently known as the strongest acis, are analyzed and compared with other species classified as superacids as well as with selected mineral acids and carbocations. Calculations (B3LYP/6-311++G(d,p) level) on these moieties as well as on their conjugate bases were performed to evaluate corresponding proton affinities. In addition, the complexes of these species with the CHB11F11(-) anion and the complexes of the conjugate bases with the trimethylammonium cation were analyzed. The scales, based on spectroscopic results, DFT energies and on the topological QTAIM (Quantum Theory of Atoms in Molecules) parameters, are introduced and discussed to order the acidity of the species analyzed here. The properties of the bond critical points corresponding to the intermolecular contacts are discussed. The majority of the results show that HCHB11F11 carborane acid is the strongest in agreement with the previous experimental studies of Reed and coworkers. Very often the abovementioned acidity scales show that carborane acids are able to protonate hydrocarbons. PMID:27253195

  13. Complexes of carborane acids linked by strong hydrogen bonds: acidity scales.

    PubMed

    Grabowski, Sławomir J

    2016-06-28

    Carborane acids, currently known as the strongest acis, are analyzed and compared with other species classified as superacids as well as with selected mineral acids and carbocations. Calculations (B3LYP/6-311++G(d,p) level) on these moieties as well as on their conjugate bases were performed to evaluate corresponding proton affinities. In addition, the complexes of these species with the CHB11F11(-) anion and the complexes of the conjugate bases with the trimethylammonium cation were analyzed. The scales, based on spectroscopic results, DFT energies and on the topological QTAIM (Quantum Theory of Atoms in Molecules) parameters, are introduced and discussed to order the acidity of the species analyzed here. The properties of the bond critical points corresponding to the intermolecular contacts are discussed. The majority of the results show that HCHB11F11 carborane acid is the strongest in agreement with the previous experimental studies of Reed and coworkers. Very often the abovementioned acidity scales show that carborane acids are able to protonate hydrocarbons.

  14. Dissociative attachment reactions of electrons with strong acid molecules

    SciTech Connect

    Adams, N.G.; Smith, D.; Viggiano, A.A.; Paulson, J.F.; Henchman, M.J.

    1986-06-15

    Using the flowing afterglow/Langmuir probe (FALP) technique, we have determined (at variously 300 and 570 K) the dissociative attachment coefficients ..beta.. for the reactions of electrons with the common acids HNO/sub 3/ (producing NO/sup -//sub 2/) and H/sub 2/SO/sub 4/ (HSO/sup -//sub 4/), the superacids FSO/sub 3/H (FSO/sup -//sub 3/), CF/sub 3/SO/sub 3/H (CF/sub 3/SO/sup -//sub 3/), ClSO/sub 3/H (ClSO/sup -//sub 3/,Cl/sup -/), the acid anhydride (CF/sub 3/SO/sub 2/)/sub 2/O (CF/sub 3/SO/sup -//sub 3/), and the halogen halides HBr (Br/sup -/) and HI (I/sup -/). The anions formed in the reactions are those given in the parentheses. The reactions with HF and HCl were investigated, but did not occur at a measurable rate since they are very endothermic. Dissociative attachment is rapid for the common acids, the superacids, and the anhydride, the measured ..beta.. being appreciable fractions of the theoretical maximum ..beta.. for such reactions, ..beta../sub max/. The HI reaction is very fast ( ..beta..approx...beta../sub max/) but the HBr reaction occurs much more slowly because it is significantly endothermic. The data indicate that the extreme acidity of the (Bronsted-type) superacids has its equivalence in the very efficient gas-phase dissociative attachment which these species undergo when reacting with free electrons. The anions of the superacids generated in these reactions, notably FSO/sup -//sub 3/ and CF/sub 3/SO/sup -//sub 3/, are very stable (unreactive) implying exceptionally large electron affinities for the FSO/sub 3/ and CF/sub 3/SO/sub 3/ radicals.

  15. Tested Demonstrations: Comparison of Strong Acid and Weak Acid Titration Curves.

    ERIC Educational Resources Information Center

    Gilbert, George L., Ed.

    1979-01-01

    A lecture demonstration is presented for comparing titration curves. A plot of pH vs volume of strong base is produced by connecting the external output of a pH meter to a strip recorder. Thus, pH is recorded as a function of time. (BB)

  16. A novel nucleic acid analogue shows strong angiogenic activity

    SciTech Connect

    Tsukamoto, Ikuko; Sakakibara, Norikazu; Maruyama, Tokumi; Igarashi, Junsuke; Kosaka, Hiroaki; Kubota, Yasuo; Tokuda, Masaaki; Ashino, Hiromi; Hattori, Kenichi; Tanaka, Shinji; Kawata, Mitsuhiro; Konishi, Ryoji

    2010-09-03

    Research highlights: {yields} A novel nucleic acid analogue (2Cl-C.OXT-A, m.w. 284) showed angiogenic potency. {yields} It stimulated the tube formation, proliferation and migration of HUVEC in vitro. {yields} 2Cl-C.OXT-A induced the activation of ERK1/2 and MEK in HUVEC. {yields} Angiogenic potency in vivo was confirmed in CAM assay and rabbit cornea assay. {yields} A synthesized small angiogenic agent would have great clinical therapeutic value. -- Abstract: A novel nucleic acid analogue (2Cl-C.OXT-A) significantly stimulated tube formation of human umbilical endothelial cells (HUVEC). Its maximum potency at 100 {mu}M was stronger than that of vascular endothelial growth factor (VEGF), a positive control. At this concentration, 2Cl-C.OXT-A moderately stimulated proliferation as well as migration of HUVEC. To gain mechanistic insights how 2Cl-C.OXT-A promotes angiogenic responses in HUVEC, we performed immunoblot analyses using phospho-specific antibodies as probes. 2Cl-C.OXT-A induced robust phosphorylation/activation of MAP kinase ERK1/2 and an upstream MAP kinase kinase MEK. Conversely, a MEK inhibitor PD98059 abolished ERK1/2 activation and tube formation both enhanced by 2Cl-C.OXT-A. In contrast, MAP kinase responses elicited by 2Cl-C.OXT-A were not inhibited by SU5416, a specific inhibitor of VEGF receptor tyrosine kinase. Collectively these results suggest that 2Cl-C.OXT-A-induces angiogenic responses in HUVEC mediated by a MAP kinase cascade comprising MEK and ERK1/2, but independently of VEGF receptor tyrosine kinase. In vivo assay using chicken chorioallantoic membrane (CAM) and rabbit cornea also suggested the angiogenic potency of 2Cl-C.OXT-A.

  17. One-step synthesis of hydrothermally stable mesoporous aluminosilicates with strong acidity

    SciTech Connect

    Yang Dongjiang; Xu Yao Wu Dong; Sun Yuhan

    2008-09-15

    Using tetraethylorthosilicate (TEOS), polymethylhydrosiloxane (PMHS) and aluminium isopropoxide (AIP) as the reactants, through a one-step nonsurfactant route based on PMHS-TEOS-AIP co-polycondensation, hydrothermally stable mesoporous aluminosilicates with different Si/Al molar ratios were successfully prepared. All samples exclusively showed narrow pore size distribution centered at 3.6 nm. To assess the hydrothermal stability, samples were subjected to 100 deg. C distilled water for 300 h. The boiled mesoporous aluminosilicates have nearly the same N{sub 2} adsorption-desorption isotherms and the same pore size distributions as those newly synthesized ones, indicating excellent hydrothermal stability. The {sup 29}Si MAS NMR spectra confirmed that PMHS and TEOS have jointly condensed and CH{sub 3} groups have been introduced into the materials. The {sup 27}Al MAS NMR spectra indicated that Al atoms have been incorporated in the mesopore frameworks. The NH{sub 3} temperature-programmed desorption showed strong acidity. Due to the existence of large amount of CH{sub 3} groups, the mesoporous aluminosilicates obtained good hydrophobicity. Owing to the relatively large pore and the strong acidity provided by the uniform four-coordinated Al atoms, the excellent catalytic performance for 1,3,5-triisopropylbenzene cracking was acquired easily. The materials may be a profitable complement for the synthesis of solid acid catalysts. - Graphical abstract: Based on the nonsurfactant method, a facile one-step synthesis route has been developed to prepare methyl-modified mesoporous aluminosilicates that possessed hydrothermal stability and strong acidity.

  18. Purification of organic acids by chromatography with strong anionic resins: Investigation of uptake mechanisms.

    PubMed

    Lemaire, Julien; Blanc, Claire-Line; Lutin, Florence; Théoleyre, Marc-André; Stambouli, Moncef; Pareau, Dominique

    2016-08-01

    Bio-based organic acids are promising renewable carbon sources for the chemical industry. However energy-consuming purification processes are used, like distillation or crystallization, to reach high purities required in some applications. That is why preparative chromatography was studied as an alternative separation technique. In a previous work dealing with the purification of lactic, succinic and citric acids, the Langmuir model was insufficient to explain the elution profiles obtained with a strong anionic resin. Consequently the Langmuir model was coupled with a usual ion-exchange model to take into account the retention of their conjugate bases (<2%), which are commonly neglected at low pH (<1.5). Elution simulations with both uptake mechanisms fitted very well with experimental pulse tests. Only two parameters were optimized (equilibrium constant of acid uptake and ion-exchange selectivity coefficient of conjugate base) and their value were coherent with experimental and resin suppliers' data. These results confirmed that the singular tailing and apparent delay observed with succinic and citric acids can be explained by the high affinity of succinate and citrate for resin cationic sites. The model was implemented in a preparative chromatography simulation program in order to optimize operating parameters of our pilot-scale ISMB unit (Improved Simulated Moving Bed). The comparison with experimental ISMB profiles was conclusive. PMID:27373374

  19. Purification of organic acids by chromatography with strong anionic resins: Investigation of uptake mechanisms.

    PubMed

    Lemaire, Julien; Blanc, Claire-Line; Lutin, Florence; Théoleyre, Marc-André; Stambouli, Moncef; Pareau, Dominique

    2016-08-01

    Bio-based organic acids are promising renewable carbon sources for the chemical industry. However energy-consuming purification processes are used, like distillation or crystallization, to reach high purities required in some applications. That is why preparative chromatography was studied as an alternative separation technique. In a previous work dealing with the purification of lactic, succinic and citric acids, the Langmuir model was insufficient to explain the elution profiles obtained with a strong anionic resin. Consequently the Langmuir model was coupled with a usual ion-exchange model to take into account the retention of their conjugate bases (<2%), which are commonly neglected at low pH (<1.5). Elution simulations with both uptake mechanisms fitted very well with experimental pulse tests. Only two parameters were optimized (equilibrium constant of acid uptake and ion-exchange selectivity coefficient of conjugate base) and their value were coherent with experimental and resin suppliers' data. These results confirmed that the singular tailing and apparent delay observed with succinic and citric acids can be explained by the high affinity of succinate and citrate for resin cationic sites. The model was implemented in a preparative chromatography simulation program in order to optimize operating parameters of our pilot-scale ISMB unit (Improved Simulated Moving Bed). The comparison with experimental ISMB profiles was conclusive.

  20. Morphologies Observed in Ultraflexible Microemulsions with and without the Presence of a Strong Acid.

    PubMed

    Lopian, Tobias; Schöttl, Sebastian; Prévost, Sylvain; Pellet-Rostaing, Stéphane; Horinek, Dominik; Kunz, Werner; Zemb, Thomas

    2016-07-27

    We show that three different morphologies exist near the two-phase boundary of ternary systems containing a hydrotropic cosolvent. Based on synchrotron small- and wide-angle X-ray scattering combined with molecular dynamics, we rationalize the specific scattering signature of direct, bicontinuous, and reverse mesoscale solubilization. Surprisingly, these mesostructures are resilient toward strong acids, which are required in industrial applications. However, on a macroscopic scale, the phase boundary shifts in salting-in and salting-out in the direct and respectively reverse regime, leading to a crossing of the binodals. PMID:27504493

  1. Morphologies Observed in Ultraflexible Microemulsions with and without the Presence of a Strong Acid

    PubMed Central

    2016-01-01

    We show that three different morphologies exist near the two-phase boundary of ternary systems containing a hydrotropic cosolvent. Based on synchrotron small- and wide-angle X-ray scattering combined with molecular dynamics, we rationalize the specific scattering signature of direct, bicontinuous, and reverse mesoscale solubilization. Surprisingly, these mesostructures are resilient toward strong acids, which are required in industrial applications. However, on a macroscopic scale, the phase boundary shifts in salting-in and salting-out in the direct and respectively reverse regime, leading to a crossing of the binodals. PMID:27504493

  2. Comparison of Four Strong Acids on the Precipitation Potential of Gypsum in Brines During Distillation of Pretreated, Augmented Urine

    NASA Technical Reports Server (NTRS)

    Muirhead, Dean

    2011-01-01

    Two batches of nominally pretreated and augmented urine were prepared with the baseline pretreatment formulation of sulfuric acid and chromium trioxide. The urine was augmented with inorganic salts and organic compounds in order to simulate a urinary ionic concentrations representing the upper 95 percentile on orbit. Three strong mineral acids: phosphoric, hydrochloric, and nitric acid, were substituted for the sulfuric acid for comparison to the baseline sulfuric acid pretreatment formulation. Three concentrations of oxidizer in the pretreatment formulation were also tested. Pretreated urine was distilled to 85% water recovery to determine the effect of each acid and its conjugate base on the precipitation of minerals during distillation. The brines were analyzed for calcium and sulfate ion, total, volatile, and fixed suspended solids. Test results verified that substitution of phosphoric, hydrochloric, or nitric acids for sulfuric acid would prevent the precipitation of gypsum up to 85% recovery from pretreated urine representing the upper 95 percentile calcium concentration on orbit.

  3. Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 2. Major structures

    USGS Publications Warehouse

    Leenheer, J.A.; Wershaw, R. L.; Reddy, M.M.

    1995-01-01

    Polycarboxylic acid structures that account for the strong-acid characteristics (pKa1 near 2.0) were examined for fulvic acid from the Suwannee River. Studies of model compounds demonstrated that pKa values near 2.0 occur only if the ??-ether or ??-ester groups were in cyclic structures with two to three additional electronegative functional groups (carboxyl, ester, ketone, aromatic groups) at adjacent positions on the ring. Ester linkage removal by alkaline hydrolysis and destruction of ether linkages through cleavage and reduction with hydriodic acid confirmed that the strong carboxyl acidity in fulvic acid was associated with polycarboxylic ??-ether and ??-ester structures. Studies of hypothetical structural models of fulvic acid indicated possible relation of these polycarboxylic structures with the amphiphilic and metal-binding properties of fulvic acid.

  4. Sulfonic acid-functionalized α-zirconium phosphate single-layer nanosheets as a strong solid acid for heterogeneous catalysis applications.

    PubMed

    Zhou, Yingjie; Huang, Rongcai; Ding, Fuchuan; Brittain, Alex D; Liu, Jingjing; Zhang, Meng; Xiao, Min; Meng, Yuezhong; Sun, Luyi

    2014-05-28

    Solid acids have received considerable attention as alternatives to traditional corrosive and hazardous homogeneous acids because of their advantages in practical applications, including their low corrosion of equipment and high catalytic activity and recyclability. In this work, a strong solid acid was prepared by anchoring thiol group terminated chains on layered α-zirconium phosphate (ZrP) single-layer nanosheets, followed by oxidation of thiol groups to form sulfonic acid groups. The obtained solid acids were thoroughly characterized and the results proved that sulfonic acid group terminated chains were successfully grafted onto the ZrP nanosheets with a high loading density. Such a strong solid acid based on inorganic nanosheets can be well-dispersed in polar solvents, leading to high accessibility to the acid functional groups. Meanwhile, it can be easily separated from the dispersion system by centrifugation or filtration. The strong solid acid can serve as an effective heterogeneous catalyst for various reactions, including the Bayer-Villiger oxidation of cyclohexanone to ε-caprolactone in the absence of organic solvents.

  5. Insights into How Students Learn the Difference between a Weak Acid and a Strong Acid from Cartoon Tutorials Employing Visualizations

    ERIC Educational Resources Information Center

    Kelly, Resa M.; Akaygun, Sevil

    2016-01-01

    This article summarizes an investigation into how Flash-based cartoon video tutorials featuring molecular visualizations affect students' mental models of acetic acid and hydrochloric acid solutions and how the acids respond when tested for electrical conductance. Variation theory served as the theoretical framework for examining how students…

  6. Eight supramolecular assemblies constructed from bis(benzimidazole) and organic acids through strong classical hydrogen bonding and weak noncovalent interactions

    NASA Astrophysics Data System (ADS)

    Jin, Shouwen; Wang, Daqi

    2014-05-01

    Eight crystalline organic acid-base adducts derived from alkane bridged bis(N-benzimidazole) and organic acids (2,4,6-trinitrophenol, p-nitrobenzoic acid, m-nitrobenzoic acid, 3,5-dinitrobenzoic acid, 5-sulfosalicylic acid and oxalic acid) were prepared and characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. Of the eight compounds five are organic salts (1, 4, 6, 7 and 8) and the other three (2, 3, and 5) are cocrystals. In all of the adducts except 1 and 8, the ratio of the acid and the base is 2:1. All eight supramolecular assemblies involve extensive intermolecular classical hydrogen bonds as well as other noncovalent interactions. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, all the complexes displayed 3D framework structure. The results presented herein indicate that the strength and directionality of the classical N+-H⋯O-, O-H⋯O, and O-H⋯N hydrogen bonds (ionic or neutral) and other nonbonding associations between acids and ditopic benzimidazoles are sufficient to bring about the formation of cocrystals or organic salts.

  7. Some investigations on the radiation stability of a strongly acidic cation exchange resin

    NASA Astrophysics Data System (ADS)

    Dessouki, A. M.; Zahran, A. H.; Rabie, A. M.; Amer, S. I.

    The radiation-chemical stability of Merck Cation Exchanger I, a strongly acidic sulphonated cation exchanger of the polymerization type based on styrene-divinylbenze (DVB) copolymers was investigated. The radiation stability of the resin was assessed from the change in exchange capacity, loss in weight, change in swelling behaviour and formation of new exchange groups. The loss in capacity was 44 and 32% for resin specimens in the H +-form irradiated to 1000 Mrad in air and in vacuum, respectively. The Na +-form of the exchanger showed high resistance to radiation and the loss in capacity did not exceed 7% at a dose of 1000 Mrad. The loss in capacity was accompanied by a loss in weight and a decrease in the degree of swelling of the irradiated resin. The formation of new functional groups of the carboxylic and phenolic types was confirmed. The amount of these group increases with the increase in the integral dose. The amount of sulphuric acid formed as a result of irradiating the resin in the dry and moist states was determined. An increase in the moisture content of the resin resulted in a marked decrease in its radiation stability.

  8. Using quantitative acid-base analysis in the ICU.

    PubMed

    Lloyd, P; Freebairn, R

    2006-03-01

    The quantitative acid-base 'Strong Ion' calculator is a practical application of quantitative acid-base chemistry, as developed by Peter Stewart and Peter Constable. It quantifies the three independent factors that control acidity, calculates the concentration and charge of unmeasured ions, produces a report based on these calculations and displays a Gamblegram depicting measured ionic species. Used together with the medical history, quantitative acid-base analysis has advantages over traditional approaches.

  9. Nacre-inspired integrated strong and tough reduced graphene oxide-poly(acrylic acid) nanocomposites.

    PubMed

    Wan, Sijie; Hu, Han; Peng, Jingsong; Li, Yuchen; Fan, Yuzun; Jiang, Lei; Cheng, Qunfeng

    2016-03-14

    Inspired by the relationship between interface interactions and the high performance mechanical properties of nacre, a strong and tough nacre-inspired nanocomposite was demonstrated based on graphene oxide (GO) and polyacrylic acid (PAA) prepared via a vacuum-assisted filtration self-assembly process. The abundant hydrogen bonding between GO and PAA results in both high strength and toughness of the bioinspired nanocomposites, which are 2 and 3.3 times higher than that of pure reduced GO film, respectively. In addition, the effect of environmental relative humidity on the mechanical properties of bioinspired nanocomposites is also investigated, and is consistent with previous theoretical predictions. Moreover, this nacre-inspired nanocomposite also displays high electrical conductivity of 108.9 S cm(-1). These excellent physical properties allow this type of nacre-inspired nanocomposite to be used in many applications, such as flexible electrodes, aerospace applications, and artificial muscles etc. This nacre-inspired strategy also opens an avenue for constructing integrated high performance graphene-based nanocomposites in the near future. PMID:26895081

  10. Nacre-inspired integrated strong and tough reduced graphene oxide-poly(acrylic acid) nanocomposites

    NASA Astrophysics Data System (ADS)

    Wan, Sijie; Hu, Han; Peng, Jingsong; Li, Yuchen; Fan, Yuzun; Jiang, Lei; Cheng, Qunfeng

    2016-03-01

    Inspired by the relationship between interface interactions and the high performance mechanical properties of nacre, a strong and tough nacre-inspired nanocomposite was demonstrated based on graphene oxide (GO) and polyacrylic acid (PAA) prepared via a vacuum-assisted filtration self-assembly process. The abundant hydrogen bonding between GO and PAA results in both high strength and toughness of the bioinspired nanocomposites, which are 2 and 3.3 times higher than that of pure reduced GO film, respectively. In addition, the effect of environmental relative humidity on the mechanical properties of bioinspired nanocomposites is also investigated, and is consistent with previous theoretical predictions. Moreover, this nacre-inspired nanocomposite also displays high electrical conductivity of 108.9 S cm-1. These excellent physical properties allow this type of nacre-inspired nanocomposite to be used in many applications, such as flexible electrodes, aerospace applications, and artificial muscles etc. This nacre-inspired strategy also opens an avenue for constructing integrated high performance graphene-based nanocomposites in the near future.

  11. Phase transition transistors based on strongly-correlated materials

    NASA Astrophysics Data System (ADS)

    Nakano, Masaki

    2013-03-01

    The field-effect transistor (FET) provides electrical switching functions through linear control of the number of charges at a channel surface by external voltage. Controlling electronic phases of condensed matters in a FET geometry has long been a central issue of physical science. In particular, FET based on a strongly correlated material, namely ``Mott transistor,'' has attracted considerable interest, because it potentially provides gigantic and diverse electronic responses due to a strong interplay between charge, spin, orbital and lattice. We have investigated electric-field effects on such materials aiming at novel physical phenomena and electronic functions originating from strong correlation effects. Here we demonstrate electrical switching of bulk state of matter over the first-order metal-insulator transition. We fabricated FETs based on VO2 with use of a recently developed electric-double-layer transistor technique, and found that the electrostatically induced carriers at a channel surface drive all preexisting localized carriers of 1022 cm-3 even inside a bulk to motion, leading to bulk carrier delocalization beyond the electrostatic screening length. This non-local switching of bulk phases is achieved with just around 1 V, and moreover, a novel non-volatile memory like character emerges in a voltage-sweep measurement. These observations are apparently distinct from those of conventional FETs based on band insulators, capturing the essential feature of collective interactions in strongly correlated materials. This work was done in collaboration with K. Shibuya, D. Okuyama, T. Hatano, S. Ono, M. Kawasaki, Y. Iwasa, and Y. Tokura. This work was supported by the Japan Society for the Promotion of Science (JSAP) through its ``Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program).''

  12. Strong Fluorescent Smart Organogel as a Dual Sensing Material for Volatile Acid and Organic Amine Vapors.

    PubMed

    Xue, Pengchong; Yao, Boqi; Wang, Panpan; Gong, Peng; Zhang, Zhenqi; Lu, Ran

    2015-11-23

    An L-phenylalanine derivative (C12PhBPCP) consisting of a strong emission fluorophore with benzoxazole and cyano groups is designed and synthesized to realize dual responses to volatile acid and organic amine vapors. The photophysical properties and self-assembly of the said derivative in the gel phase are also studied. C12PhBPCP can gelate organic solvents and self-assemble into 1 D nanofibers in the gels. UV/Vis absorption spectral results show H-aggregate formation during gelation, which indicates strong exciton coupling between fluorophores. Both wet gel and xerogel emit strong green fluorescence because the cyano group suppresses fluorescence quenching in the self-assemblies. Moreover, the xerogel film with strong green fluorescence can be used as a dual chemosensor for quantitative detection of volatile acid and organic amine vapors with fast response times and low detection limits owing to its large surface area and amplified fluorescence quenching. The detection limits are 796 ppt and 25 ppb for gaseous aniline and trifluoroacetic acid (TFA), respectively.

  13. Ion-exchange equilibrium of N-acetyl-D-neuraminic acid on a strong anionic exchanger.

    PubMed

    Wu, Jinglan; Ke, Xu; Zhang, Xudong; Zhuang, Wei; Zhou, Jingwei; Ying, Hanjie

    2015-09-15

    N-acetyl-D-neuraminic acid (Neu5Ac) is a high value-added product widely applied in the food industry. A suitable equilibrium model is required for purification of Neu5Ac based on ion-exchange chromatography. Hence, the equilibrium uptake of Neu5Ac on a strong anion exchanger, AD-1 was investigated experimentally and theoretically. The uptake of Neu5Ac by the hydroxyl form of the resin occurred primarily by a stoichiometric exchange of Neu5Ac(-) and OH(-). The experimental data showed that the selectivity coefficient for the exchange of Neu5Ac(-) with OH(-) was a non-constant quantity. Subsequently, the Saunders' model, which took into account the dissociation reactions of Neu5Ac and the condition of electroneutrality, was used to correlate the Neu5Ac sorption isotherms at various solution pHs and Neu5Ac concentrations. The model provided an excellent fit to the binary exchange data for Cl(-)/OH(-) and Neu5Ac(-)/OH(-), and an approximate prediction of equilibrium in the ternary system Cl(-)/Neu5Ac(-)/OH(-). This basic information combined with the general mass transfer model could lay the foundation for the prediction of dynamic behavior of fixed bed separation process afterwards.

  14. Effect of Strong Acid Functional Groups on Electrode Rise Potential in Capacitive Mixing by Double Layer Expansion

    SciTech Connect

    Hatzell, Marta C.; Raju, Muralikrishna; Watson, Valerie J.; Stack, Andrew G.; van Duin, Adri C. T.; Logan, Bruce E.

    2014-11-03

    We report that the amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10–5) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g–1) had a positive rise potential of 59 ± 4 mV in the LC solution, whereas the carbon with the highest concentration (0.36 mmol g–1) had a negative rise potential (₋31 ± 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 ± 2 mV (unaltered) to ₋6 ± 0.5 mV (oxidized), producing a whole cell potential (53 ± 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 ± 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. In conclusion, these results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons.

  15. Effect of Strong Acid Functional Groups on Electrode Rise Potential in Capacitive Mixing by Double Layer Expansion

    DOE PAGES

    Hatzell, Marta C.; Raju, Muralikrishna; Watson, Valerie J.; Stack, Andrew G.; van Duin, Adri C. T.; Logan, Bruce E.

    2014-11-03

    We report that the amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10–5) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g–1) had a positive rise potential of 59 ± 4 mV in themore » LC solution, whereas the carbon with the highest concentration (0.36 mmol g–1) had a negative rise potential (₋31 ± 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 ± 2 mV (unaltered) to ₋6 ± 0.5 mV (oxidized), producing a whole cell potential (53 ± 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 ± 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. In conclusion, these results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons.« less

  16. Effect of strong acid functional groups on electrode rise potential in capacitive mixing by double layer expansion.

    PubMed

    Hatzell, Marta C; Raju, Muralikrishna; Watson, Valerie J; Stack, Andrew G; van Duin, Adri C T; Logan, Bruce E

    2014-12-01

    The amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10(–5)) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g(–1)) had a positive rise potential of 59 ± 4 mV in the LC solution, whereas the carbon with the highest concentration (0.36 mmol g(–1)) had a negative rise potential (−31 ± 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 ± 2 mV (unaltered) to −6 ± 0.5 mV (oxidized), producing a whole cell potential (53 ± 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 ± 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. These results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons. PMID:25365360

  17. The first proton sponge-based amino acids: synthesis, acid-base properties and some reactivity.

    PubMed

    Ozeryanskii, Valery A; Gorbacheva, Anastasia Yu; Pozharskii, Alexander F; Vlasenko, Marina P; Tereznikov, Alexander Yu; Chernov'yants, Margarita S

    2015-08-21

    The first hybrid base constructed from 1,8-bis(dimethylamino)naphthalene (proton sponge or DMAN) and glycine, N-methyl-N-(8-dimethylamino-1-naphthyl)aminoacetic acid, was synthesised in high yield and its hydrobromide was structurally characterised and used to determine the acid-base properties via potentiometric titration. It was found that the basic strength of the DMAN-glycine base (pKa = 11.57, H2O) is on the level of amidine amino acids like arginine and creatine and its structure, zwitterionic vs. neutral, based on the spectroscopic (IR, NMR, mass) and theoretical (DFT) approaches has a strong preference to the zwitterionic form. Unlike glycine, the DMAN-glycine zwitterion is N-chiral and is hydrolytically cleaved with the loss of glycolic acid on heating in DMSO. This reaction together with the mild decarboxylative conversion of proton sponge-based amino acids into 2,3-dihydroperimidinium salts under air-oxygen was monitored with the help of the DMAN-alanine amino acid. The newly devised amino acids are unique as they combine fluorescence, strongly basic and redox-active properties.

  18. The first proton sponge-based amino acids: synthesis, acid-base properties and some reactivity.

    PubMed

    Ozeryanskii, Valery A; Gorbacheva, Anastasia Yu; Pozharskii, Alexander F; Vlasenko, Marina P; Tereznikov, Alexander Yu; Chernov'yants, Margarita S

    2015-08-21

    The first hybrid base constructed from 1,8-bis(dimethylamino)naphthalene (proton sponge or DMAN) and glycine, N-methyl-N-(8-dimethylamino-1-naphthyl)aminoacetic acid, was synthesised in high yield and its hydrobromide was structurally characterised and used to determine the acid-base properties via potentiometric titration. It was found that the basic strength of the DMAN-glycine base (pKa = 11.57, H2O) is on the level of amidine amino acids like arginine and creatine and its structure, zwitterionic vs. neutral, based on the spectroscopic (IR, NMR, mass) and theoretical (DFT) approaches has a strong preference to the zwitterionic form. Unlike glycine, the DMAN-glycine zwitterion is N-chiral and is hydrolytically cleaved with the loss of glycolic acid on heating in DMSO. This reaction together with the mild decarboxylative conversion of proton sponge-based amino acids into 2,3-dihydroperimidinium salts under air-oxygen was monitored with the help of the DMAN-alanine amino acid. The newly devised amino acids are unique as they combine fluorescence, strongly basic and redox-active properties. PMID:26159785

  19. The Roles of Acids and Bases in Enzyme Catalysis

    ERIC Educational Resources Information Center

    Weiss, Hilton M.

    2007-01-01

    Many organic reactions are catalyzed by strong acids or bases that protonate or deprotonate neutral reactants leading to reactive cations or anions that proceed to products. In enzyme reactions, only weak acids and bases are available to hydrogen bond to reactants and to transfer protons in response to developing charges. Understanding this…

  20. Thermoresponsive anionic copolymer brushes containing strong acid moieties for effective separation of basic biomolecules and proteins.

    PubMed

    Nagase, Kenichi; Kobayashi, Jun; Kikuchi, Akihiko; Akiyama, Yoshikatsu; Kanazawa, Hideko; Okano, Teruo

    2014-10-13

    A thermoresponsive copolymer brush possessing the sulfonic acid group, poly(N-isopropylacrylamide (IPAAm)-co-2-acrylamido-2-methylpropanesulfonic acid (AMPS)-co-tert-butylacrylamide (tBAAm)), was grafted onto the surface of silica beads through surface-initiated atom transfer radical polymerization. Prepared copolymer and copolymer brushes on silica beads were characterized by observing the phase transition profile, CHNS elemental analysis, X-ray photoelectron spectroscopy, and gel permeation chromatography. The phase transition profile indicated that an appropriate AMPS composition for enabling thermally modulated property changes is 5 mol %, while excessive amounts of sulfonic acid groups prevented copolymer phase transition. Chromatographic elutions of catecholamine derivatives and basic proteins were observed, using the prepared copolymer brush-modified beads as chromatographic matrices, and the results suggest that the beads interact with these analytes through relatively strong electrostatic interactions. Thus, poly(IPAAm-co-AMPS-co-tBAAm) brush-modified beads will be useful for effective thermoresponsive chromatography matrices that separate basic biomolecules through strong electrostatic interactions. PMID:25220634

  1. Regeneration of strong-base anion-exchange resins by sequential chemical displacement

    DOEpatents

    Brown, Gilbert M.; Gu, Baohua; Moyer, Bruce A.; Bonnesen, Peter V.

    2002-01-01

    A method for regenerating strong-base anion exchange resins utilizing a sequential chemical displacement technique with new regenerant formulation. The new first regenerant solution is composed of a mixture of ferric chloride, a water-miscible organic solvent, hydrochloric acid, and water in which tetrachloroferrate anion is formed and used to displace the target anions on the resin. The second regenerant is composed of a dilute hydrochloric acid and is used to decompose tetrachloroferrate and elute ferric ions, thereby regenerating the resin. Alternative chemical displacement methods include: (1) displacement of target anions with fluoroborate followed by nitrate or salicylate and (2) displacement of target anions with salicylate followed by dilute hydrochloric acid. The methodology offers an improved regeneration efficiency, recovery, and waste minimization over the conventional displacement technique using sodium chloride (or a brine) or alkali metal hydroxide.

  2. Molten fatty acid based microemulsions.

    PubMed

    Noirjean, Cecile; Testard, Fabienne; Dejugnat, Christophe; Jestin, Jacques; Carriere, David

    2016-06-21

    We show that ternary mixtures of water (polar phase), myristic acid (MA, apolar phase) and cetyltrimethylammonium bromide (CTAB, cationic surfactant) studied above the melting point of myristic acid allow the preparation of microemulsions without adding a salt or a co-surfactant. The combination of SANS, SAXS/WAXS, DSC, and phase diagram determination allows a complete characterization of the structures and interactions between components in the molten fatty acid based microemulsions. For the different structures characterized (microemulsion, lamellar or hexagonal phases), a similar thermal behaviour is observed for all ternary MA/CTAB/water monophasic samples and for binary MA/CTAB mixtures without water: crystalline myristic acid melts at 52 °C, and a thermal transition at 70 °C is assigned to the breaking of hydrogen bounds inside the mixed myristic acid/CTAB complex (being the surfactant film in the ternary system). Water determines the film curvature, hence the structures observed at high temperature, but does not influence the thermal behaviour of the ternary system. Myristic acid is partitioned in two "species" that behave independently: pure myristic acid and myristic acid associated with CTAB to form an equimolar complex that plays the role of the surfactant film. We therefore show that myristic acid plays the role of a solvent (oil) and a co-surfactant allowing the fine tuning of the structure of oil and water mixtures. This solvosurfactant behaviour of long chain fatty acid opens the way for new formulations with a complex structure without the addition of any extra compound. PMID:27241163

  3. Water O–H Stretching Raman Signature for Strong Acid Monitoring via Multivariate Analysis

    SciTech Connect

    Casella, Amanda J.; Levitskaia, Tatiana G.; Peterson, James M.; Bryan, Samuel A.

    2013-04-16

    Spectroscopic techniques have been applied extensively for quantification and analysis of solution compositions. In addition to static measurements, these techniques have been implemented in flow systems providing real-time solution information. A distinct need exists for information regarding acid concentration as it affects extraction efficiency and selectivity of many separation processes. Despite of the seeming simplicity of the problem, no practical solution has been offered yet particularly for the large-scale schemes involving toxic streams such as highly radioactive nuclear wastes. Classic potentiometric technique is not amiable for on-line measurements in nuclear fuel reprocessing due to requirements of frequent calibration/maintenance and poor long-term stability in the aggressive chemical and radiation environments. In this work, the potential of using Raman spectroscopic measurements for on-line monitoring of strong acid concentration in the solutions relevant to the dissolved used fuel was investigated. The Raman water signature was monitored and recorded for nitric and hydrochloric acid solution systems of systematically varied chemical composition, ionic strength, and temperature. The generated Raman spectroscopic database was used to develop predictive chemometric models for the quantification of the acid concentration (H+), neodymium concentration (Nd3+), nitrate concentration (NO3-), density, and ionic strength. This approach was validated using a flow solvent extraction system.

  4. Providing Climate Policy Makers With a Strong Scientific Base (Invited)

    NASA Astrophysics Data System (ADS)

    Struzik, E.

    2009-12-01

    Scientists can and should inform public policy decisions in the Arctic. But the pace of climate change in the polar world has been occurring far more quickly than most scientists have been able to predict. This creates problems for decision-makers who recognize that difficult management decisions have to be made in matters pertaining to wildlife management, cultural integrity and economic development. With sea ice melting, glaciers receding, permafrost thawing, forest fires intensifying, and disease and invasive species rapidly moving north, the challenge for scientists to provide climate policy makers with a strong scientific base has been daunting. Clashing as this data sometimes does with the “traditional knowledge” of indigenous peoples in the north, it can also become very political. As a result the need to effectively communicate complex data is more imperative now than ever before. Here, the author describes how the work of scientists can often be misinterpreted or exploited in ways that were not intended. Examples include the inappropriate use of scientific data in decision-making on polar bears, caribou and other wildlife populations; the use of scientific data to debunk the fact that greenhouse gases are driving climate change, and the use of scientific data to position one scientist against another when there is no inherent conflict. This work will highlight the need for climate policy makers to increase support for scientists working in the Arctic, as well as illustrate why it is important to find new and more effective ways of communicating scientific data. Strategies that might be considered by granting agencies, scientists and climate policy decision-makers will also be discussed.

  5. Potentiometric Acid-Base Titrations with Activated Graphite Electrodes

    NASA Astrophysics Data System (ADS)

    Riyazuddin, P.; Devika, D.

    1997-10-01

    Dry cell graphite (DCG) electrodes activated with potassium permanganate are employed as potentiometric indicator electrodes for acid-base titrations. Special attention is given to an indicator probe comprising activated DCG-non-activiated DCG electrode couple. This combination also proves suitable for the titration of strong or weak acids.

  6. Modern quantitative acid-base chemistry.

    PubMed

    Stewart, P A

    1983-12-01

    Quantitative analysis of ionic solutions in terms of physical and chemical principles has been effectively prohibited in the past by the overwhelming amount of calculation it required, but computers have suddenly eliminated that prohibition. The result is an approach to acid-base which revolutionizes our ability to understand, predict, and control what happens to hydrogen ions in living systems. This review outlines that approach and suggests some of its most useful implications. Quantitative understanding requires distinctions between independent variables (in body fluids: pCO2, net strong ion charge, and total weak acid, usually protein), and dependent variables [( HCO-3], [HA], [A-], [CO(2-)3], [OH-], and [H+] (or pH]. Dependent variables are determined by independent variables, and can be calculated from the defining equations for the specific system. Hydrogen ion movements between solutions can not affect hydrogen ion concentration; only changes in independent variables can. Many current models for ion movements through membranes will require modification on the basis of this quantitative analysis. Whole body acid-base balance can be understood quantitatively in terms of the three independent variables and their physiological regulation by the lungs, kidneys, gut, and liver. Quantitative analysis also shows that body fluids interact mainly by strong ion movements through the membranes separating them.

  7. Investigating the Weak to Evaluate the Strong: An Experimental Determination of the Electron Binding Energy of Carborane Anions and the Gas phase Acidity of Carborane Acids

    SciTech Connect

    Meyer, Matthew M; Wang, Xue B; Reed, Christopher A; Wang, Lai S; Kass, Steven R

    2009-12-23

    Five CHB11X6Y5- carborane anions from the series X = Br, Cl, I and Y = H, Cl, CH3 were generated by electrospray ionization, and their reactivity with a series of Brønsted acids and electron transfer reagents were examined in the gas phase. The undecachlorocarborane acid, H(CHB11Cl11), was found to be far more acidic than the former record holder, (1-C4F9SO2)2NH (i.e., ΔH°acid = 241 ± 29 vs 291.1 ± 2.2 kcal mol-1) and bridges the gas-phase acidity and basicity scales for the first time. Its conjugate base, CHB11Cl11-, was found by photoelectron spectroscopy to have a remarkably large electron binding energy (6.35 ± 0.02 eV) but the value for the (1-C4F9SO2)2N- anion is even larger (6.5 ± 0.1 eV). Consequently, it is the weak H-(CHB11Cl11) BDE (70.0 kcal mol-1, G3(MP2)) compared to the strong BDE of (1-C4F9SO2)2N-H (127.4 ± 3.2 kcal mol-1) that accounts for the greater acidity of carborane acids.

  8. The comparative effects of gamma radiation and in situ alpha particles on five strong-base anion exchange resins

    SciTech Connect

    Marsh, S.F.

    1991-01-01

    The effects of external gamma radiation and in situ alpha particles were measured on a recently available, macroporous, strong-base polyvinylpyridine resin and on four strong-base polystyrene anion exchange resins. Each resin was irradiated in 7 M nitric acid to 1--10 megaGray of gamma radiation from external {sup 60}Co, or to 5--14 megaGray of alpha particles from sorbed {sup 238}Pu. Each irradiated resin was measured for changes in dry weight, wet volume, weak-base and strong-base chloride exchange capacities, and exchange capacities for Pu(4) from nitric acid. Alpha-induced resin damage was significantly less than that caused by an equivalent dose of gamma radiation. The polyvinylpyridine resin offers the greatest resistance to damage from gamma radiation and from alpha particles. 5 refs., 1 figs. 5 tabs.

  9. Nucleic acid based logical systems.

    PubMed

    Han, Da; Kang, Huaizhi; Zhang, Tao; Wu, Cuichen; Zhou, Cuisong; You, Mingxu; Chen, Zhuo; Zhang, Xiaobing; Tan, Weihong

    2014-05-12

    Researchers increasingly visualize a significant role for artificial biochemical logical systems in biological engineering, much like digital logic circuits in electrical engineering. Those logical systems could be utilized as a type of servomechanism to control nanodevices in vitro, monitor chemical reactions in situ, or regulate gene expression in vivo. Nucleic acids (NA), as carriers of genetic information with well-regulated and predictable structures, are promising materials for the design and engineering of biochemical circuits. A number of logical devices based on nucleic acids (NA) have been designed to handle various processes for technological or biotechnological purposes. This article focuses on the most recent and important developments in NA-based logical devices and their evolution from in vitro, through cellular, even towards in vivo biological applications.

  10. Mesoporous aluminosilicates with ordered hexagonal structure, strong acidity, and extraordinary hydrothermal stability at high temperatures.

    PubMed

    Zhang, Z; Han, Y; Xiao, F S; Qiu, S; Zhu, L; Wang, R; Yu, Y; Zhang, Z; Zou, B; Wang, Y; Sun, H; Zhao, D; Wei, Y

    2001-05-30

    Highly ordered hexagonal mesoporous aluminosilicates (MAS-5) with uniform pore sizes have been successfully synthesized from assembly of preformed aluminosilcate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The aluminosilicate precursors were obtained by heating, at 100--140 degrees C for 2--10 h, aluminasilica gels at the Al(2)O(3)/SiO(2)/TEAOH/H(2)O molar ratios of 1.0/7.0--350/10.0--33.0/500--2000. Mesoporous MAS-5 shows extraordinary stability both in boiling water (over 300 h) and in steam (800 degrees C for 2 h). Temperature-programmed desorption of ammonia shows that the acidic strength of MAS-5 is much higher than that of MCM-41 and is comparable to that of microporous Beta zeolite. In catalytic cracking of 1,3,5-triisopropylbenzene and alkylation of isobutane with butene, MAS-5 exhibits greater catalytic activity and selectivity, as compared with MCM-41 and HZSM-5. The MAS-5 samples were characterized with infrared, UV--Raman, and NMR spectroscopy and numerous other techniques. The results suggest that MAS-5 consists of both mesopores and micropores and that the pore walls of MAS-5 contain primary and secondary structural building units, similar to those of microporous zeolites. Such unique structural features might be responsible for the observed strong acidity and high thermal stability of the mesoporous aluminosilicates with well-ordered hexagonal symmetry.

  11. Kinetics and Thermodynamics of Reserpine Adsorption onto Strong Acidic Cationic Exchange Fiber

    PubMed Central

    Guo, Zhanjing; Liu, Xiongmin; Huang, Hongmiao

    2015-01-01

    The kinetics and thermodynamics of the adsorption process of reserpine adsorbed onto the strong acidic cationic exchange fiber (SACEF) were studied by batch adsorption experiments. The adsorption capacity strongly depended on pH values, and the optimum reserpine adsorption onto the SACEF occurred at pH = 5 of reserpine solution. With the increase of temperature and initial concentration, the adsorption capacity increased. The equilibrium was attained within 20 mins. The adsorption process could be better described by the pseudo-second-order model and the Freundlich isotherm model. The calculated activation energy Ea was 4.35 kJ/mol. And the thermodynamic parameters were: 4.97<ΔH<7.44 kJ/mol, -15.29<ΔG<-11.87 kJ/mol and 41.97<ΔS<47.35 J/mol·K. The thermodynamic parameters demonstrated that the adsorption was an endothermic, spontaneous and feasible process of physisorption within the temperature range between 283 K and 323 K and the initial concentration range between 100 mg/L and 300 mg/L. All the results showed that the SACEF had a good adsorption performance for the adsorption of reserpine from alcoholic solution. PMID:26422265

  12. Radiometric acid-base titrations.

    PubMed

    Erdey, L; Gimesi, O; Szabadváry, F

    1969-03-01

    Acid-base titrations can be performed with radiometric end-point detection by use of labelled metal salts (e.g., ZnCl(2), HgCl(2)). Owing to the formation or dissolution of the corresponding hydroxide after the equivalence point, the activity of the titrated solution linearly increases or decreases as excess of standard solution is added. The end-point of the titration is determined graphically.

  13. Use of an Acid-Base Table.

    ERIC Educational Resources Information Center

    Willis, Grover; And Others

    1986-01-01

    Identifies several ways in which an acid-base table can provide students with information about chemical reactions. Cites examples of the chart's use and includes a table which indicates the strengths of some common acids and bases. (ML)

  14. Dissolution of the Argonne Premium Coal Samples in strong base

    SciTech Connect

    Winans, R.E.; McBeth, R.L.; Hunt, J.E.

    1993-03-01

    The objective of this study is to solubilize the Argoruie Premium Coal Samples in order to facilitate analysis by mass spectrometry, FTIR and NMR. Earlier, in a search for relatively mild methods for solubilizing coal, we discovered that treating coals with potassium hydroxide in ethylene glycol at 250{degrees}C to be quite an effective approach. Under these conditions, secondary reactions which may obscure the distribution of the basic building blocks of the coal structure are not expected to occur. At higher temperatures, such as those used in more traditional liquefaction processes ({gt} 400{degrees}C), secondary reactions such as the formation of polycyclic aromatic and heteroaromatic compounds dominate. A focus of our approach to characterization of coals is desorption-pyrolysis high resolution CI and EI mass spectrometry and laser desorption mass spectrpmetry (LDMS). It has been shown by PyMS that the yields and the distribution of products is superior for coal extracts compared to the original whole coals. There appears tobe few secondary reactions occurring and many molecules, which are released in analysis of the extract, are trapped in the solid matrix of the coal and never observed. In addition, soluble materials are more amenable to LDMS. The glycol/KOH system was chosen since in early work up to 93% of the product was soluble for lower-rank bituminous coals. Others have solubilized coals under basic conditions. Ouchi and co-workers used ethanolic - NaOH at temperatures ranging from 260{degrees}C to 450{degrees}C. More recently, Stock and coworkers have discussed the use of Lochmann`s base (potassium tert-butoxide, n-butyl lithium in heptane at reflux) which is especially effective for the higher rank coals. Also, a base hydrolysis is included in a low severity liquefaction scheme devised by Shabtai and coworkers.

  15. Dissolution of the Argonne Premium Coal Samples in strong base

    SciTech Connect

    Winans, R.E.; McBeth, R.L.; Hunt, J.E.

    1993-01-01

    The objective of this study is to solubilize the Argoruie Premium Coal Samples in order to facilitate analysis by mass spectrometry, FTIR and NMR. Earlier, in a search for relatively mild methods for solubilizing coal, we discovered that treating coals with potassium hydroxide in ethylene glycol at 250[degrees]C to be quite an effective approach. Under these conditions, secondary reactions which may obscure the distribution of the basic building blocks of the coal structure are not expected to occur. At higher temperatures, such as those used in more traditional liquefaction processes ([gt] 400[degrees]C), secondary reactions such as the formation of polycyclic aromatic and heteroaromatic compounds dominate. A focus of our approach to characterization of coals is desorption-pyrolysis high resolution CI and EI mass spectrometry and laser desorption mass spectrpmetry (LDMS). It has been shown by PyMS that the yields and the distribution of products is superior for coal extracts compared to the original whole coals. There appears tobe few secondary reactions occurring and many molecules, which are released in analysis of the extract, are trapped in the solid matrix of the coal and never observed. In addition, soluble materials are more amenable to LDMS. The glycol/KOH system was chosen since in early work up to 93% of the product was soluble for lower-rank bituminous coals. Others have solubilized coals under basic conditions. Ouchi and co-workers used ethanolic - NaOH at temperatures ranging from 260[degrees]C to 450[degrees]C. More recently, Stock and coworkers have discussed the use of Lochmann's base (potassium tert-butoxide, n-butyl lithium in heptane at reflux) which is especially effective for the higher rank coals. Also, a base hydrolysis is included in a low severity liquefaction scheme devised by Shabtai and coworkers.

  16. Isolation of a thermostable acid phytase from Aspergillus niger UFV-1 with strong proteolysis resistance.

    PubMed

    Monteiro, Paulo S; Guimarães, Valéria M; de Melo, Ricardo R; de Rezende, Sebastião T

    2015-03-01

    An Aspergillus niger UFV-1 phytase was characterized and made available for industrial application. The enzyme was purified via ultrafiltration followed by acid precipitation, ion exchange and gel filtration chromatography. This protein exhibited a molecular mass of 161 kDa in gel filtration and 81 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), indicating that it may be a dimer. It presented an optimum temperature of 60 °C and optimum pH of 2.0. The K M for sodium phytate hydrolysis was 30.9 mM, while the k cat and k cat / K M were 1.46 ×10 (5) s (-1) and 4.7 × 10 (6) s (-1) .M (-1) , respectively. The purified phytase exhibited broad specificity on a range of phosphorylated compounds, presenting activity on sodium phytate, p-NPP, 2- naphthylphosphate, 1- naphthylphosphate, ATP, phenyl-phosphate, glucose-6-phosphate, calcium phytate and other substrates. Enzymatic activity was slightly inhibited by Mg (2+) , Cd (2+) , K (+) and Ca (2+) , and it was drastically inhibited by F (-) . The enzyme displayed high thermostability, retaining more than 90% activity at 60 °C during 120 h and displayed a t 1/2 of 94.5 h and 6.2 h at 70 °C and 80 °C, respectively. The enzyme demonstrated strong resistance toward pepsin and trypsin, and it retained more than 90% residual activity for both enzymes after 1 h treatment. Additionally, the enzyme efficiently hydrolyzed phytate in livestock feed, liberating 15.3 μmol phosphate/mL after 2.5 h of treatment. PMID:26221114

  17. Isolation of a thermostable acid phytase from Aspergillus niger UFV-1 with strong proteolysis resistance

    PubMed Central

    Monteiro, Paulo S.; Guimarães, Valéria M.; de Melo, Ricardo R.; de Rezende, Sebastião T.

    2015-01-01

    An Aspergillus niger UFV-1 phytase was characterized and made available for industrial application. The enzyme was purified via ultrafiltration followed by acid precipitation, ion exchange and gel filtration chromatography. This protein exhibited a molecular mass of 161 kDa in gel filtration and 81 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), indicating that it may be a dimer. It presented an optimum temperature of 60 °C and optimum pH of 2.0. The K M for sodium phytate hydrolysis was 30.9 mM, while the k cat and k cat / K M were 1.46 ×10 5 s −1 and 4.7 × 10 6 s −1 .M −1 , respectively. The purified phytase exhibited broad specificity on a range of phosphorylated compounds, presenting activity on sodium phytate, p-NPP, 2- naphthylphosphate, 1- naphthylphosphate, ATP, phenyl-phosphate, glucose-6-phosphate, calcium phytate and other substrates. Enzymatic activity was slightly inhibited by Mg 2+ , Cd 2+ , K + and Ca 2+ , and it was drastically inhibited by F − . The enzyme displayed high thermostability, retaining more than 90% activity at 60 °C during 120 h and displayed a t 1/2 of 94.5 h and 6.2 h at 70 °C and 80 °C, respectively. The enzyme demonstrated strong resistance toward pepsin and trypsin, and it retained more than 90% residual activity for both enzymes after 1 h treatment. Additionally, the enzyme efficiently hydrolyzed phytate in livestock feed, liberating 15.3 μmol phosphate/mL after 2.5 h of treatment. PMID:26221114

  18. Photocurable bioadhesive based on lactic acid.

    PubMed

    Marques, D S; Santos, J M C; Ferreira, P; Correia, T R; Correia, I J; Gil, M H; Baptista, C M S G

    2016-01-01

    Novel photocurable and low molecular weight oligomers based on l-lactic acid with proven interest to be used as bioadhesive were successfully manufactured. Preparation of lactic acid oligomers with methacrylic end functionalizations was carried out in the absence of catalyst or solvents by self-esterification in two reaction steps: telechelic lactic acid oligomerization with OH end groups and further functionalization with methacrylic anhydride. The final adhesive composition was achieved by the addition of a reported biocompatible photoinitiator (Irgacure® 2959). Preliminary in vitro biodegradability was investigated by hydrolytic degradation in PBS (pH=7.4) at 37 °C. The adhesion performance was evaluated using glued aminated substrates (gelatine pieces) subjected to pull-to-break test. Surface energy measured by contact angles is lower than the reported values of the skin and blood. The absence of cytoxicity was evaluated using human fibroblasts. A notable antimicrobial behaviour was observed using two bacterial models (Staphylococcus aureus and Escherichia coli). The cured material exhibited a strong thrombogenic character when placed in contact with blood, which can be predicted as a haemostatic effect for bleeding control. This novel material was subjected to an extensive characterization showing great potential for bioadhesive or other biomedical applications where biodegradable and biocompatible photocurable materials are required. PMID:26478350

  19. Characterization and diagenesis of strong-acid carboxyl groups in humic substances

    USGS Publications Warehouse

    Leenheer, J.A.; Wershaw, R. L.; Brown, G.K.; Reddy, M.M.

    2003-01-01

    A small fraction of carboxylic acid functional groups in humic substances are exceptionally acidic with pKa values as low as 0.5. A review of acid-group theory eliminated most models and explanations for these exceptionally acidic carboxyl groups. These acidic carboxyl groups in Suwannee River fulvic acid were enriched by a 2-stage fractionation process and the fractions were characterized by elemental, molecular-weight, and titrimetric analyses, and by infrared and 13C- and 1H-nuclear magnetic resonance spectrometry. An average structural model of the most acidic fraction derived from the characterization data indicated a high density of carboxyl groups clustered on oxygen-heterocycle alicyclic rings. Intramolecular H-bonding between adjacent carboxyl groups in these ring structures enhanced stabilization of the carboxylate anion which results in low pKa1 values. The standard, tetrahydrofuran tetracarboxylic acid, was shown to have similar acidity characteristics to the highly acidic fulvic acid fraction. The end products of 3 known diagenetic pathways for the formation of humic substances were shown to result in carboxyl groups clustered on oxygen-heterocycle alicyclic rings.

  20. Zeta-crystallin displays strong selectivity for salicylic acid over aspirin.

    PubMed

    Bazzi, Mohammad D

    2002-04-26

    Interaction of camel lens zeta-crystallin with aspirin was investigated by activity and fluorescence measurements. Aspirin minimally inhibited the oxidoreductase activity of the enzyme and weakly quenched its fluorescence. However, significant fluorescence quenching of zeta-crystallin coincided with the appearance of a fluorescence signal characteristic of salicylic acid thereby raising the possibility that salicylic acid might have been the moiety responsible for inhibition and fluorescence quenching. Direct fluorescence measurements showed that zeta-crystallin had a much higher affinity for salicylic acid than aspirin (K(i) of about 24 microM for salicylic acid versus 630 microM for aspirin). Salicylic acid was also far more effective in inhibiting zeta-crystallin than aspirin (K(i) values were 23 microM versus 820 microM, respectively). Inhibition kinetics suggested that salicylic acid interacted with zeta-crystallin via a binding site that was distinct from that of NADPH. Salicylic acid also interacted with and quenched the fluorescence of camel lens alpha-crystallin suggesting a general mode of interaction with lens proteins. Within the normal therapeutic concentrations of salicylic acid or aspirin, only crystallin-salicylic acid interactions might be significant. These results showed that camel lens zeta- and alpha-crystallin exhibited remarkable selectivity for salicylic acid over aspirin, and thus, could be considered as salicylate-binding proteins.

  1. Detection of methylglyoxal as a degradation product of DNA and nucleic acid components treated with strong acid.

    PubMed

    Chaplen, F W; Fahl, W E; Cameron, D C

    1996-05-01

    The 1,2-diaminobenzene derivation assay for methylglyoxal in biological systems involves the use of perchloric acid, both as a deproteinizing agent and to prevent the spontaneous formation of methylglyoxal from glycolytic pathway intermediates. However, while using a modification of the standard literature assay to measure methylglyoxal in Chinese hamster ovary cells, we found that oxidation of nucleic acids and related compounds by perchloric or trichloroacetic acid results in the formation of methylglyoxal. Compounds containing 2-deoxyribose gave higher levels of methylglyoxal than those containing ribose; purine nucleotides and deoxynucleotides gave more methylglyoxal than did the pyrimidines. Nucleic acids were the most susceptible to degradation, with 12-fold more methylglyoxal being formed from DNA than RNA. Oxidation of nucleic acids increased with higher temperatures and with decreasing nucleic acid fragment size. Another product of nucleic acid oxidation was 2,3-butanedione, the 1,2-diaminobenzene derivative of which is sometimes used as an internal standard during methylglyoxal measurement. Unless accounted for during the assay procedure, the generation of methylglyoxal and 2,3-butanedione due to the oxidation of nucleic acids may lead to substantial errors in the determination of methylglyoxal concentrations in biological systems.

  2. Preparation of highly charged cellulose nanofibrils using high-pressure homogenization coupled with strong acid hydrolysis pretreatments.

    PubMed

    Tian, Cuihua; Yi, Jianan; Wu, Yiqiang; Wu, Qinglin; Qing, Yan; Wang, Lijun

    2016-01-20

    Cellulose nanofibrils (CNFs) are attracting much attention for the advantages of excellent mechanical strength, good optical transparency, and high surface area. An eco-friendly and energy-saving method was created in this work to produce highly negative charged CNFs using high-pressure mechanical defibrillation coupled with strong acid hydrolysis pretreatments. The morphological development, zeta potential, crystal structure, chemical composition and thermal degradation behavior of the resultant materials were evaluated by transmission electron microscopy (TEM), zeta potential analysis, X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), and thermogravimetric analysis (TGA). These CNFs were fully separated, surface-charged, and highly entangled. They showed a large fiber aspect ratio compared to traditional cellulose nanocrystrals that are produced by strong acid hydrolysis. Compared to hydrochloric acid hydrolysis, the CNFs produced by sulfuric acid pretreatments were completely defibrillated and presented stable suspensions (or gels) even at low fiber content. On the other hand, CNFs pretreated by hydrochloric acid hydrolysis trended to aggregate because of the absence of surface charge. The crystallinity index (CI) of CNFs decreased because of mechanical defibrillation, and then increased dramatically with increased sulfuric acid concentration and reaction time. FTIR analysis showed that the C-O-SO3 group was introduced on the surfaces of CNFs during sulfuric acid hydrolysis. These sulfate groups accelerated the thermal degradation of CNFs, which occurred at lower temperature than wood pulp, indicating that the thermal stability of sulfuric acid hydrolyzed CNFs was decreased. The temperature of the maximum decomposition rate (Tmax) and the maximum weight-loss rates (MWLRmax) were much lower than for wood pulp because of the retardant effect of sulfuric acid during the combustion of CNFs. By contrast, the CNFs treated with hydrochloric acid

  3. Evaluation of DNA typing as a positive identification method for soft and hard tissues immersed in strong acids.

    PubMed

    Robino, C; Pazzi, M; Di Vella, G; Martinelli, D; Mazzola, L; Ricci, U; Testi, R; Vincenti, M

    2015-11-01

    Identification of human remains can be hindered by several factors (e.g., traumatic mutilation, carbonization or decomposition). Moreover, in some criminal cases, offenders may purposely adopt various expedients to thwart the victim's identification, including the dissolution of body tissues by the use of corrosive reagents, as repeatedly reported in the past for Mafia-related murders. By means of an animal model, namely porcine samples, we evaluated standard DNA typing as a method for identifying soft (muscle) and hard (bone and teeth) tissues immersed in strong acids (hydrochloric, nitric and sulfuric acid) or in mixtures of acids (aqua regia). Samples were tested at different time intervals, ranging between 2 and 6h (soft tissues) and 2-28 days (hard tissues). It was shown that, in every type of acid, complete degradation of the DNA extracted from soft tissues preceded tissue dissolution and could be observed within 4h of immersion. Conversely, high molecular weight DNA amenable to STR analysis could be isolated from hard tissues as long as cortical bone fragments were still present (28 days for sulfuric acid, 7 days for nitric acid, 2 days for hydrochloric acid and aqua regia), or the integrity of the dental pulp chamber was preserved (7 days, in sulfuric acid only). The results indicate that DNA profiling of acid-treated body parts (in particular, cortical bone) is still feasible at advanced stages of corrosion, even when the morphological methods used in forensic anthropology and odontology can no longer be applied for identification purposes.

  4. Strong Hydrogen Bonded Molecular Interactions between Atmospheric Diamines and Sulfuric Acid.

    PubMed

    Elm, Jonas; Jen, Coty N; Kurtén, Theo; Vehkamäki, Hanna

    2016-05-26

    We investigate the molecular interaction between methyl-substituted N,N,N',N'-ethylenediamines, propane-1,3-diamine, butane-1,4-diamine, and sulfuric acid using computational methods. Molecular structure of the diamines and their dimer clusters with sulfuric acid is studied using three density functional theory methods (PW91, M06-2X, and ωB97X-D) with the 6-31++G(d,p) basis set. A high level explicitly correlated CCSD(T)-F12a/VDZ-F12 method is used to obtain accurate binding energies. The reaction Gibbs free energies are evaluated and compared with values for reactions involving ammonia and atmospherically relevant monoamines (methylamine, dimethylamine, and trimethylamine). We find that the complex formation between sulfuric acid and the studied diamines provides similar or more favorable reaction free energies than dimethylamine. Diamines that contain one or more secondary amino groups are found to stabilize sulfuric acid complexes more efficiently. Elongating the carbon backbone from ethylenediamine to propane-1,3-diamine or butane-1,4-diamine further stabilizes the complex formation with sulfuric acid by up to 4.3 kcal/mol. Dimethyl-substituted butane-1,4-diamine yields a staggering formation free energy of -19.1 kcal/mol for the clustering with sulfuric acid, indicating that such diamines could potentially be a key species in the initial step in the formation of new particles. For studying larger clusters consisting of a diamine molecule with up to four sulfuric acid molecules, we benchmark and utilize a domain local pair natural orbital coupled cluster (DLPNO-CCSD(T)) method. We find that a single diamine is capable of efficiently stabilizing sulfuric acid clusters with up to four acid molecules, whereas monoamines such as dimethylamine are capable of stabilizing at most 2-3 sulfuric acid molecules. PMID:27128188

  5. Crystal and molecular structure of eight organic acid-base adducts from 2-methylquinoline and different acids

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Jin, Shouwen; Tao, Lin; Liu, Bin; Wang, Daqi

    2014-08-01

    Eight supramolecular complexes with 2-methylquinoline and acidic components as 4-aminobenzoic acid, 2-aminobenzoic acid, salicylic acid, 5-chlorosalicylic acid, 3,5-dinitrosalicylic acid, malic acid, sebacic acid, and 1,5-naphthalenedisulfonic acid were synthesized and characterized by X-ray crystallography, IR, mp, and elemental analysis. All of the complexes are organic salts except compound 2. All supramolecular architectures of 1-8 involve extensive classical hydrogen bonds as well as other noncovalent interactions. The results presented herein indicate that the strength and directionality of the classical hydrogen bonds (ionic or neutral) between acidic components and 2-methylquinoline are sufficient to bring about the formation of binary organic acid-base adducts. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, the complexes 1-8 displayed 2D-3D framework structure.

  6. Origin of the 900 cm{sup −1} broad double-hump OH vibrational feature of strongly hydrogen-bonded carboxylic acids

    SciTech Connect

    Van Hoozen, Brian L.; Petersen, Poul B.

    2015-03-14

    Medium and strong hydrogen bonds are common in biological systems. Here, they provide structural support and can act as proton transfer relays to drive electron and/or energy transfer. Infrared spectroscopy is a sensitive probe of molecular structure and hydrogen bond strength but strongly hydrogen-bonded structures often exhibit very broad and complex vibrational bands. As an example, strong hydrogen bonds between carboxylic acids and nitrogen-containing aromatic bases commonly display a 900 cm{sup −1} broad feature with a remarkable double-hump structure. Although previous studies have assigned this feature to the OH, the exact origin of the shape and width of this unusual feature is not well understood. In this study, we present ab initio calculations of the contributions of the OH stretch and bend vibrational modes to the vibrational spectrum of strongly hydrogen-bonded heterodimers of carboxylic acids and nitrogen-containing aromatic bases, taking the 7-azaindole—acetic acid and pyridine—acetic acid dimers as examples. Our calculations take into account coupling between the OH stretch and bend modes as well as how both of these modes are affected by lower frequency dimer stretch modes, which modulate the distance between the monomers. Our calculations reproduce the broadness and the double-hump structure of the OH vibrational feature. Where the spectral broadness is primarily caused by the dimer stretch modes strongly modulating the frequency of the OH stretch mode, the double-hump structure results from a Fermi resonance between the out of the plane OH bend and the OH stretch modes.

  7. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1995-09-12

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  8. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1995-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  9. Content of chalconaringenin and chlorogenic acid in cherry tomatoes is strongly reduced during postharvest ripening.

    PubMed

    Slimestad, Rune; Verheul, Michèl J

    2005-09-01

    The contents of chalconaringenin, chlorogenic acid, rutin, ascorbic acid, lycopene, and beta-carotene were analyzed during postharvest and vine ripening of cherry tomatoes (Lycopersicon esculentumMill.) (cv. Jennita) produced in a greenhouse. A remarkable decrease in the content of chalconaringenin took place during postharvest ripening. The tomatoes were found to contain 15.26 mg 100 g(-1) fresh weight (FW) at harvest but held only 0.41 mg after 3 weeks at 20 degrees C in darkness. Chalconaringenin did not convert into naringenin. The content of chlorogenic acid fell from 0.51 to 0.06 mg 100 g(-1) FW at the same conditions. The content of rutin and that of total phenolics remained stable during postharvest ripening. The amounts of lycopene as well as beta-carotene and ascorbic acid increased during postharvest ripening. No significant change in the amount of methanol soluble antioxidants or total soluble solids was found during postharvest ripening of the tomato fruits. During vine ripening, the total amount of phenolics and that of soluble solids (% Brix) increased. The content of phenolics correlated well with the content of methanol soluble antioxidants (p < 0.001). The amount of ascorbic acid increased from 9.7 mg in green-yellow tomatoes to 17.1 mg 100 g(-1) FW in red tomatoes. The amount of chalconaringenin decreased to 8.16 mg 100 g(-1) FW, whereas no significant change was observed for chlorogenic acid or rutin. Possible causes for the decrease in chalconaringenin are discussed.

  10. Students' Alternate Conceptions on Acids and Bases

    ERIC Educational Resources Information Center

    Pan, Hanqing; Henriques, Laura

    2015-01-01

    Knowing what students bring to the classroom can and should influence how we teach them. This study is a review of the literature associated with secondary and postsecondary students' ideas about acids and bases. It was found that there are six types of alternate ideas about acids and bases that students hold. These are: macroscopic properties of…

  11. The Kidney and Acid-Base Regulation

    ERIC Educational Resources Information Center

    Koeppen, Bruce M.

    2009-01-01

    Since the topic of the role of the kidneys in the regulation of acid base balance was last reviewed from a teaching perspective (Koeppen BM. Renal regulation of acid-base balance. Adv Physiol Educ 20: 132-141, 1998), our understanding of the specific membrane transporters involved in H+, HCO , and NH transport, and especially how these…

  12. The Conjugate Acid-Base Chart.

    ERIC Educational Resources Information Center

    Treptow, Richard S.

    1986-01-01

    Discusses the difficulties that beginning chemistry students have in understanding acid-base chemistry. Describes the use of conjugate acid-base charts in helping students visualize the conjugate relationship. Addresses chart construction, metal ions, buffers and pH titrations, and the organic functional groups and nonaqueous solvents. (TW)

  13. Preparation and characterization of high capacity, strong cation-exchange fiber based adsorbents.

    PubMed

    Schwellenbach, Jan; Taft, Florian; Villain, Louis; Strube, Jochen

    2016-05-20

    Motivated by the demand for more economical capture and polishing steps in downstream processing of protein therapeutics, a novel strong cation-exchange chromatography stationary phase based on polyethylene terephthalate (PET) high surface area short-cut fibers is presented. The fiber surface is modified by grafting glycidyl methacrylate (GMA) via surface-initiated atom transfer radical polymerization (SI-ATRP) and a subsequent derivatization leading to sulfonic acid groups. The obtained cation-exchange fibers have been characterized and compared to commercially available resin and membrane based adsorbers. High volumetric static binding capacities for lysozyme (90mg/mL) and polyclonal human IgG (hIgG, 92mg/mL) were found, suggesting an efficient multi-layer binding within the grafted hydrogel layer. A packed bed of randomly orientated fibers has been tested for packing efficiency, permeability and chromatographic performance. High dynamic binding capacities for lysozyme (50mg/mL) and hIgG (54mg/mL) were found nearly independent of the bed-residence time, revealing a fast mass-transport mechanism. Height equivalent to a theoretical plate (HETP) values in the order of 0.1 cm and a peak asymmetry factor (AF) of 1.8 have been determined by tracer experiments. Additionally inverse size-exclusion chromatography (iSEC) revealed a bimodal structure within the fiber bed, consisting of larger transport channels, formed by the voidage between the fibers, and a hydrogel layer with porous properties. PMID:27106396

  14. Geochemical modelling of EGS fracture stimulation applying weak and strong acid treatments

    NASA Astrophysics Data System (ADS)

    Sigfusson, Bergur; Sif Pind Aradottir, Edda

    2015-04-01

    Engineered Geothermal systems (EGS) provide geothermal power by tapping into the Earth's deep geothermal resources that are otherwise not exploitable due to lack of water and fractures, location or rock type. EGS technologies have the potential to cost effectively produce large amounts of electricity almost anywhere in the world. The EGS technology creates permeability in the rock by hydro-fracturing the reservoir with cold water pumped into the first well (the injection well) at a high pressure. The second well (the production well) intersects the stimulated fracture system and returns the hot water to the surface where electricity can be generated. A significant technological hurdle is ensuring effective connection between the wells and the fracture system and to control the deep-rooted fractures (can exceed 5 000 m depth). A large area for heat transfer and sufficient mass flow needs to be ensured between wells without creating fast flowing paths in the fracture network. Maintaining flow through the fracture system can cause considerable energy penalty to the overall process. Therefore, chemical methods to maintain fractures and prevent scaling can be necessary to prevent excessive pressure build up in the re-injection wells of EGS systems. The effect of different acid treatments on the porosity development of selected rock types was simulated with the aid of the Petrasim interface to the Toughreact simulation code. The thermodynamic and kinetic database of Aradottir et al. (2014) was expanded to include new minerals and the most important fluoride bearing species involved in mineral reactions during acid stimulation of geothermal systems. A series of simulations with injection waters containing fluoric acid, hydrochloric acid and CO2 or mixtures thereof were then carried out and porosity development in the fracture system monitored. The periodic injection of weak acid mixtures into EGS systems may be cost effective in some isolated cases to prevent pressure

  15. Dissociation of a strong acid in neat solvents: diffusion is observed after reversible proton ejection inside the solvent shell.

    PubMed

    Veiga-Gutiérrez, Manoel; Brenlla, Alfonso; Carreira Blanco, Carlos; Fernández, Berta; Kovalenko, Sergey A; Rodríguez-Prieto, Flor; Mosquera, Manuel; Lustres, J Luis Pérez

    2013-11-14

    Strong-acid dissociation was studied in alcohols. Optical excitation of the cationic photoacid N-methyl-6-hydroxyquinolinium triggers proton transfer to the solvent, which was probed by spectral reconstruction of picosecond fluorescence traces. The process fulfills the classical Eigen-Weller mechanism in two stages: (a) solvent-controlled reversible dissociation inside the solvent shell and (b) barrierless splitting of the encounter complex. This can be appreciated only when fluorescence band integrals are used to monitor the time evolution of the reactant and product concentrations. Band integrals are insensitive to solvent dynamics and report relative concentrations directly. This was demonstrated by first measuring the fluorescence decay of the conjugate base across the full emission band, independently of the proton-transfer reaction. Multiexponential decay curves at single wavelengths result from a dynamic red shift of fluorescence in the course of solvent relaxation, whereas clean single exponential decays are obtained if the band integral is monitored instead. The extent of the shift is consistent with previously reported femtosecond transient absorption measurements, continuum theory of solvatochromism, and molecular properties derived from quantum chemical calculations. In turn, band integrals show clean biexponential decay of the photoacid and triexponential evolution of the conjugate base in the course of the proton transfer to solvent reaction. The dissociation step follows the slowest stage of solvation, which was measured here independently by picosecond fluorescence spectroscopy in five aliphatic alcohols. Also, the rate constant of the encounter-complex splitting stage is compatible with proton diffusion. Thus, for this photoacid, both stages reach the highest possible rates: solvation and diffusion control. Under these conditions, the concentration of the encounter complex is substantial during the earliest nanosecond.

  16. Sequential injection redox or acid-base titration for determination of ascorbic acid or acetic acid.

    PubMed

    Lenghor, Narong; Jakmunee, Jaroon; Vilen, Michael; Sara, Rolf; Christian, Gary D; Grudpan, Kate

    2002-12-01

    Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence of peak area obtained with ascorbic acid concentration up to 1200 mg l(-1) was achieved. The relative standard deviation for 11 replicate determinations of 400 mg l(-1) ascorbic acid was 2.9%. The second system, for acetic acid determination, was based on acid-base titration of acetic acid with sodium hydroxide using phenolphthalein as an indicator. The decrease in color intensity of the indicator was proportional to the acid content. A linear calibration graph in the range of 2-8% w v(-1) of acetic acid with a relative standard deviation of 4.8% (5.0% w v(-1) acetic acid, n=11) was obtained. Sample throughputs of 60 h(-1) were achieved for both systems. The systems were successfully applied for the assays of ascorbic acid in vitamin C tablets and acetic acid content in vinegars, respectively.

  17. Electrochemical nanomaterial-based nucleic acid aptasensors.

    PubMed

    Palchetti, Ilaria; Mascini, Marco

    2012-04-01

    Recent progress in the development of electrochemical nanomaterial-aptamer-based biosensors is summarized. Aptamers are nucleic acid ligands that can be generated against amino acids, drugs, proteins, and other molecules. They are isolated from a large random library of synthetic nucleic acids by an iterative process of binding, separation, and amplification, called systematic evolution of ligands by exponential enrichment (SELEX). In this review, different methods of integrating aptamers with different nanomaterials and nanoparticles for electrochemical biosensing application are described.

  18. Bioavailability of heavy metals in strongly acidic soils treated with exceptional quality biosolids

    SciTech Connect

    Basta, N.T.; Sloan, J.J.

    1999-03-01

    New federal regulations may increase application of exceptional quality (EQ) biosolids to acidic soils, and information on the effect of this practice on bioavailability of heavy metal is limited. The objective of this study was to compare bioavailability of heavy metal in soil treated with nonalkaline or alkaline EQ biosolids with limestone-treated soils. Three acidic soils (pH 3.7--4.3) were treated with three amounts of lime-stabilized biosolids (LS), anaerobic-digested biosolids (AN), or agricultural limestone (L), and incubated at 25 C. Soil solution Cd, Zn, and other chemical constituents were measured at 1, 30, 90, and 180 d incubation. Soil solution Cd and Zn were AN > LS {ge} L, C. Soil solution Cd and Zn increased with AN applied but decreased wit h LS applied. The high application of LS had soil solution Zn dramatically decreased at soil pH > 5.5 and >5.1, respectively. Soil solution Cd and Zn increases were AN > LS with incubation time. Biosolids treatments increased heavy metal in Ca(NO{sub 3}){sub 2} and NaOAc fractions. Except for Cd, most metal from biosolids were in EDTA and HNO{sub 3} fractions. Heavy metal bioavailability, measured using lettuce (Latuca sativa L.), was AN > LS {ge} L, C. Although state regulations prohibiting application of nonalkaline EQ biosolids to acidic soil is a prudent practice, application of EQ alkaline biosolids that achieves soil pH > 5 minimizes risk from soil solution Cd and Zn and plant uptake of heavy metal.

  19. Disinfective process of strongly acidic electrolyzed product of sodium chloride solution against Mycobacteria.

    PubMed

    Yamamoto, Tomoyo Matsushita; Nakano, Takashi; Yamaguchi, Masaki; Shimizu, Mitsuhide; Wu, Hong; Aoki, Hiroaki; Ota, Rie; Kobayashi, Toyohide; Sano, Kouichi

    2012-12-01

    Electrolyzed acid water (EAW) has been studied for its disinfective potential against pathogenic microbes; however, the bactericidal process against Mycobacteria has not been clearly presented. In this study, to clarify the disinfective process against Mycobacteria, EAW-treated bacteria were examined against laboratory strains of Mycobacterium bovis (M. bovis), Mycobacterium smegmatis (M. smegmatis), and Mycobacterium terrae (M. terrae) by recovery culture and observation of morphology, enzymatic assay, and the detection of DNA. All experiments were performed with the use of EAW containing 30 ppm free chlorine that kills Mycobacteria, including three pathogenic clinical isolates of Mycobacterium tuberculosis (M. tuberculosis) and six isolates of other Mycobacteria, within 5 min. In morphology, the bacterial surface became rough, and a longitudinal concavity-like structure appeared. The intrabacterial enzyme of EAW-contacted bacteria was inactivated, but chromosomal DNA was not totally denatured. These results suggest that the bactericidal effect of EAW against Mycobacteria occurs by degradation of the cell wall, followed by denaturation of cytoplasmic proteins, but degeneration of the nucleic acid is not always necessary.

  20. Disinfective process of strongly acidic electrolyzed product of sodium chloride solution against Mycobacteria.

    PubMed

    Yamamoto, Tomoyo Matsushita; Nakano, Takashi; Yamaguchi, Masaki; Shimizu, Mitsuhide; Wu, Hong; Aoki, Hiroaki; Ota, Rie; Kobayashi, Toyohide; Sano, Kouichi

    2012-12-01

    Electrolyzed acid water (EAW) has been studied for its disinfective potential against pathogenic microbes; however, the bactericidal process against Mycobacteria has not been clearly presented. In this study, to clarify the disinfective process against Mycobacteria, EAW-treated bacteria were examined against laboratory strains of Mycobacterium bovis (M. bovis), Mycobacterium smegmatis (M. smegmatis), and Mycobacterium terrae (M. terrae) by recovery culture and observation of morphology, enzymatic assay, and the detection of DNA. All experiments were performed with the use of EAW containing 30 ppm free chlorine that kills Mycobacteria, including three pathogenic clinical isolates of Mycobacterium tuberculosis (M. tuberculosis) and six isolates of other Mycobacteria, within 5 min. In morphology, the bacterial surface became rough, and a longitudinal concavity-like structure appeared. The intrabacterial enzyme of EAW-contacted bacteria was inactivated, but chromosomal DNA was not totally denatured. These results suggest that the bactericidal effect of EAW against Mycobacteria occurs by degradation of the cell wall, followed by denaturation of cytoplasmic proteins, but degeneration of the nucleic acid is not always necessary. PMID:23224598

  1. Base-acid hybrid water electrolysis.

    PubMed

    Chen, Long; Dong, Xiaoli; Wang, Fei; Wang, Yonggang; Xia, Yongyao

    2016-02-21

    A base-acid hybrid electrolytic system with a low onset voltage of 0.78 V for water electrolysis was developed by using a ceramic Li-ion exchange membrane to separate the oxygen-evolving reaction (OER) in a basic electrolyte solution containing the Li-ion and hydrogen-evolving reaction (HER) in an acidic electrolyte solution. PMID:26804323

  2. Strong and Biostable Hyaluronic Acid-Calcium Phosphate Nanocomposite Hydrogel via in Situ Precipitation Process.

    PubMed

    Jeong, Seol-Ha; Koh, Young-Hag; Kim, Suk-Wha; Park, Ji-Ung; Kim, Hyoun-Ee; Song, Juha

    2016-03-14

    Hyaluronic acid (HAc) hydrogel exhibits excellent biocompatibility, but it has limited biomedical application due to its poor biomechanical properties as well as too-fast enzymatic degradation. In this study, we have developed an in situ precipitation process for the fabrication of a HAc-calcium phosphate nanocomposite hydrogel, after the formation of the glycidyl methacrylate-conjugated HAc (GMHA) hydrogels via photo-cross-linking, to improve the mechanical and biological properties under physiological conditions. In particular, our process facilitates the rapid incorporation of calcium phosphate (CaP) nanoparticles of uniform size and with minimal agglomeration into a polymer matrix, homogeneously. Compared with pure HAc, the nanocomposite hydrogels exhibit improved mechanical behavior. Specifically, the shear modulus is improved by a factor of 4. The biostability of the nanocomposite hydrogel was also significantly improved compared with that of pure HAc hydrogels under both in vitro and in vivo conditions. PMID:26878437

  3. VAMP/synaptobrevin cleavage by tetanus and botulinum neurotoxins is strongly enhanced by acidic liposomes.

    PubMed

    Caccin, Paola; Rossetto, Ornella; Rigoni, Michela; Johnson, Eric; Schiavo, Giampietro; Montecucco, Cesare

    2003-05-01

    Tetanus and botulinum neurotoxins (TeNT and BoNTs) block neuroexocytosis via specific cleavage and inactivation of SNARE proteins. Such activity is exerted by the N-terminal 50 kDa light chain (L) domain, which is a zinc-dependent endopeptidase. TeNT, BoNT/B, /D, /F and /G cleave vesicle associated membrane protein (VAMP), a protein of the neurotransmitter-containing small synaptic vesicles, at different single peptide bonds. Since the proteolytic activity of these metalloproteases is higher on native VAMP inserted in synaptic vesicles than on recombinant VAMP, we have investigated the influence of liposomes of different lipid composition on this activity. We found that the rate of VAMP cleavage with all neurotoxins tested here is strongly enhanced by negatively charged lipid mixtures. This effect is at least partially due to the binding of the metalloprotease to the lipid membranes, with electrostatic interactions playing an important role.

  4. Jammed acid-base reactions at interfaces.

    PubMed

    Gibbs-Davis, Julianne M; Kruk, Jennifer J; Konek, Christopher T; Scheidt, Karl A; Geiger, Franz M

    2008-11-19

    Using nonlinear optics, we show that acid-base chemistry at aqueous/solid interfaces tracks bulk pH changes at low salt concentrations. In the presence of 10 to 100 mM salt concentrations, however, the interfacial acid-base chemistry remains jammed for hours, until it finally occurs within minutes at a rate that follows the kinetic salt effect. For various alkali halide salts, the delay times increase with increasing anion polarizability and extent of cation hydration and lead to massive hysteresis in interfacial acid-base titrations. The resulting implications for pH cycling in these systems are that interfacial systems can spatially and temporally lag bulk acid-base chemistry when the Debye length approaches 1 nm.

  5. Comparison of Four Strong Acids on the Precipitation Potential of Gypsum in Brines During Distillation of Pretreated, Augmented Urine

    NASA Technical Reports Server (NTRS)

    Muirhead, Dean; Carrier, Christopher

    2012-01-01

    In this study, three different mineral acids were substituted for sulfuric acid (H2SO4) in the urine stabilizer solution to eliminate the excess of sulfate ions in pretreated urine and assess the impact on maximum water recovery to avoid precipitation of minerals during distillation. The study evaluated replacing 98% sulfuric acid with 85% phosphoric acid (H3PO4), 37% hydrochloric acid (HCl), or 70% nitric acid (HNO3). The effect of lowering the oxidizer concentration in the pretreatment formulation also was studied. This paper summarizes the test results, defines candidate formulations for further study, and specifies the injection masses required to stabilize urine and minimize the risk of mineral precipitation during distillation. In the first test with a brine ersatz acidified with different acids, the solubility of calcium in gypsum saturated solutions was measured. The solubility of gypsum was doubled in the brines acidified with the alternative acids compared to sulfuric acid. In a second series of tests, the alternative acid pretreatment concentrations were effective at preventing precipitation of gypsum and other minerals up to 85% water recovery from 95th-percentile pretreated, augmented urine. Based on test results, phosphoric acid is recommended as the safest alternative to sulfuric acid. It also is recommended that the injected mass concentration of chromium trioxide solution be reduced by 75% to minimize liquid resupply mass by about 50%, reduce toxicity of brines, and reduce the concentration of organic acids in distillate. The new stabilizer solution formulations and required doses to stabilize urine and prevent precipitation of minerals up to 85% water recovery are given. The formulations in this study were tested on a limited number of artificially augmented urine batches collected from employees at the Johnson Space Center (JSC). This study successfully demonstrated that the desired physical and chemical stability of pretreated urine and brines

  6. Acid-Base Titration of (S)-Aspartic Acid: A Circular Dichroism Spectrophotometry Experiment

    NASA Astrophysics Data System (ADS)

    Cavaleiro, Ana M. V.; Pedrosa de Jesus, Júlio D.

    2000-09-01

    The magnitude of the circular dichroism of (S)-aspartic acid in aqueous solutions at a fixed wavelength varies with the addition of strong base. This laboratory experiment consists of the circular dichroism spectrophotometric acid-base titration of (S)-aspartic acid in dilute aqueous solutions, and the use of the resulting data to determine the ionization constant of the protonated amino group. The work familiarizes students with circular dichroism and illustrates the possibility of performing titrations using a less usual instrumental method of following the course of a reaction. It shows the use of a chiroptical property in the determination of the concentration in solution of an optically active molecule, and exemplifies the use of a spectrophotometric titration in the determination of an ionization constant.

  7. A Direct, Biomass-Based Synthesis of Benzoic Acid: Formic Acid-Mediated Deoxygenation of the Glucose-Derived Materials Quinic Acid and Shikimic Acid

    SciTech Connect

    Arceo, Elena; Ellman, Jonathan; Bergman, Robert

    2010-05-03

    An alternative biomass-based route to benzoic acid from the renewable starting materials quinic acid and shikimic acid is described. Benzoic acid is obtained selectively using a highly efficient, one-step formic acid-mediated deoxygenation method.

  8. A strong integrated strength and toughness artificial nacre based on dopamine cross-linked graphene oxide.

    PubMed

    Cui, Wei; Li, Mingzhu; Liu, Jiyang; Wang, Ben; Zhang, Chuck; Jiang, Lei; Cheng, Qunfeng

    2014-09-23

    Demands of the strong integrated materials have substantially increased across various industries. Inspired by the relationship of excellent integration of mechanical properties and hierarchical nano/microscale structure of the natural nacre, we have developed a strategy for fabricating the strong integrated artificial nacre based on graphene oxide (GO) sheets by dopamine cross-linking via evaporation-induced assembly process. The tensile strength and toughness simultaneously show 1.5 and 2 times higher than that of natural nacre. Meanwhile, the artificial nacre shows high electrical conductivity. This type of strong integrated artificial nacre has great potential applications in aerospace, flexible supercapacitor electrodes, artificial muscle, and tissue engineering. PMID:25106494

  9. New Y-function based MOSFET parameter extraction method from weak to strong inversion range

    NASA Astrophysics Data System (ADS)

    Henry, J. B.; Rafhay, Q.; Cros, A.; Ghibaudo, G.

    2016-09-01

    A new Y-function based MOSFET parameter extraction method is proposed. This method relies on explicit expressions of inversion charge and drain current versus Yc(=Qi√Cgc)-function and Y(=Id/√gm)-function, respectively, applicable from weak to strong inversion range. It enables a robust MOSFET parameter extraction even for low gate voltage overdrive, whereas conventional extraction techniques relying on strong inversion approximation fail.

  10. Preparation and evaluation of rigid porous polyacrylamide-based strong cation-exchange monolithic columns for capillary electrochromatography.

    PubMed

    Dong, Jing; Ou, Junjie; Dong, Xiaoli; Wu, Renan; Ye, Mingliang; Zou, Hanfa

    2007-11-01

    A CEC monolithic column with strong cation-exchange (SCX) stationary phase based on hydrophilic monomers was prepared by in situ polymerization of acrylamide, methylenebisacrylamide, and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) in a complete organic binary porogenic solvent consisting of DMSO and dodecanol. The sulfonic groups provided by the monomer AMPS on the surface of the stationary phase generate an EOF from anode to cathode, and serve as an SCX stationary phase at the same time. The monolithic stationary phase exhibited normal-phase chromatographic behavior for neutral analytes. For charged analytes, electrostatic interaction/repulsion with the monolith was observed. The strong SCX monolithic column has been successfully employed in the electrochromatographic separation of basic drugs, peptides, and alkaloids extracted from natural products.

  11. Preparation and evaluation of rigid porous polyacrylamide-based strong cation-exchange monolithic columns for capillary electrochromatography.

    PubMed

    Dong, Jing; Ou, Junjie; Dong, Xiaoli; Wu, Renan; Ye, Mingliang; Zou, Hanfa

    2007-11-01

    A CEC monolithic column with strong cation-exchange (SCX) stationary phase based on hydrophilic monomers was prepared by in situ polymerization of acrylamide, methylenebisacrylamide, and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) in a complete organic binary porogenic solvent consisting of DMSO and dodecanol. The sulfonic groups provided by the monomer AMPS on the surface of the stationary phase generate an EOF from anode to cathode, and serve as an SCX stationary phase at the same time. The monolithic stationary phase exhibited normal-phase chromatographic behavior for neutral analytes. For charged analytes, electrostatic interaction/repulsion with the monolith was observed. The strong SCX monolithic column has been successfully employed in the electrochromatographic separation of basic drugs, peptides, and alkaloids extracted from natural products. PMID:17924588

  12. [Kidney, Fluid, and Acid-Base Balance].

    PubMed

    Shioji, Naohiro; Hayashi, Masao; Morimatsu, Hiroshi

    2016-05-01

    Kidneys play an important role to maintain human homeostasis. They contribute to maintain body fluid, electrolytes, and acid-base balance. Especially in fluid control, we, physicians can intervene body fluid balance using fluid resuscitation and diuretics. In recent years, one type of fluid resuscitation, hydroxyl ethyl starch has been extensively studied in the field of intensive care. Although their effects on fluid resuscitation are reasonable, serious complications such as kidney injury requiring renal replacement therapy occur frequently. Now we have to pay more attention to this important complication. Another topic of fluid management is tolvaptan, a selective vasopressin-2 receptor antagonist Recent randomized trial suggested that tolvaptan has a similar supportive effect for fluid control and more cost effective compared to carperitide. In recent years, Stewart approach is recognized as one important tool to assess acid-base balance in critically ill patients. This approach has great value, especially to understand metabolic components in acid-base balance. Even for assessing the effects of kidneys on acid-base balance, this approach gives us interesting insight. We should appropriately use this new approach to treat acid-base abnormality in critically ill patients. PMID:27319095

  13. Acid-base disorders in calves with chronic diarrhea.

    PubMed

    Bednarski, M; Kupczyński, R; Sobiech, P

    2015-01-01

    The aim of this study was to analyze disorders of acid-base balance in calves with chronic diarrhea caused by mixed, viral, bacterial and Cryptosporydium parvum infection. We compared results ob- tained with the classic model (Henderson-Hasselbalch) and strong ion approach (the Steward model). The study included 36 calves aged between 14 and 21 days. The calves were allocated to three groups: I - (control) non-diarrheic calves, group II - animals with compensated acid-base imbalance and group III calves with compensated acid-base disorders and hypoalbuminemia. Plasma concentrations of Na+, K+, Cl-, C12+, Mg2+, P, albumin and lactate were measured. In the classic model, acid-base balance was determined on the basis of blood pH, pCO2, HCO3-, BE and anion gap. In the strong ion model, strong ion difference (SID), effective strong anion difference, total plasma concentration of nonvolatile buffers (A(Tot)) and strong ion gap (SIG) were measured. The control calves and the animals from groups II and III did not differ significantly in terms of their blood pH. The plasma concentration of HCO3-, BE and partial pressure of CO2 in animals from the two groups with chronic diarrhea were significantly higher than those found in the controls. The highest BE (6.03 mmol/l) was documented in calves from group II. The animals from this group presented compensation resulted from activation of metabolic mechanisms. The calves with hypoal- buminemia (group III) showed lower plasma concentrations of albumin (15.37 g/L), Cl (74.94 mmol/L), Mg2+ (0.53 mmol/L), P (1.41 mmol/L) and higher value of anion gap (39.03 mmol/L). This group III presented significantly higher SID3 (71.89 mmol/L), SID7 (72.92 mmol/L) and SIG (43.53 mmol/L) values than animals from the remaining groups (P < 0.01), whereas A(Tot) (6.82 mmol/L) were significantly lower. The main finding of the correlation study was the excellent relationship between the AGcorr and SID3, SID7, SIG. In conclusion, chronic diarrhea leads

  14. Comparative study on sample stacking by moving reaction boundary formed with weak acid and weak or strong alkali in capillary electrophoresis: I. Theory.

    PubMed

    Cao, Chengxi; Zhang, Wei; Fan, Liuyin; Shao, Jing; Li, Si

    2011-05-15

    The condensation of low abundance zwitterion substance, such as protein and peptide, has great significance to the study on proteomics. This paper develops the theory on design of online stacking conditions of zwitterion by a moving reaction boundary (MRB) in capillary electrophoresis (CE). This concerns the choice of running and sample buffers, velocity design of MRB, and salt effect on the stacking. The theoretical results unveil that: (1) the velocity of MRB formed with weak acidic buffer and strong alkali should be set between zero and the velocity of zwitterion in the alkali phase, or no stacking occurs; (2) if a strong alkali is used to prepare the sample, a much long front plug of strong base must be injected before the alkaline sample plug for complete stacking, whereas no such front plug is needed if a weak alkali with enough high concentration and pH value is used to prepare the sample buffer; (3) the existence of salt in sample matrix has a weak effect on the stacking of zwitterion if sample is prepared with weak alkaline buffer, while has a dramatic effect on the same stacking if with a strong base buffer. In addition, the concentration of weak alkali used for preparation of sample should be set at the point, at which the velocity of MRB is as much as possible close to that of negative zwitterion. The developed theory and its computation are quantitatively proved by the experiments of zwitterion stacking by the MRB as shown in the previous and the accompanying papers. The proposed theoretic results hold obvious significances on-column stacking of low abundance zwitterions, such as amino acid, or peptides or proteins, in CE.

  15. Acid-base properties of humic and fulvic acids formed during composting.

    PubMed

    Plaza, César; Senesi, Nicola; Polo, Alfredo; Brunetti, Gennaro

    2005-09-15

    The soil acid-base buffering capacity and the biological availability, mobilization, and transport of macro- and micronutrients, toxic metal ions, and xenobiotic organic cations in soil are strongly influenced by the acid-base properties of humic substances, of which humic and fulvic acids are the major fractions. For these reasons, the proton binding behavior of the humic acid-like (HA) and fulvic acid-like (FA) fractions contained in a compost are believed to be instrumental in its successful performance in soil. In this work, the acid-base properties of the HAs and FAs isolated from a mixture of the sludge residue obtained from olive oil mill wastewater (OMW) evaporated in an open-air pond and tree cuttings (TC) at different stages of composting were investigated by a current potentiometric titration method and the nonideal competitive adsorption (NICA)-Donnan model. The NICA-Donnan model provided an excellent description of the acid-base titration data, and pointed out substantial differences in site density and proton-binding affinity between the HAs and FAs examined. With respect to FAs, HAs were characterized by a smaller content of carboxylic- and phenolic-type groups and their larger affinities for proton binding. Further, HAs featured a greater heterogeneity in carboxylic-type groups than FAs. The composting process increased the content and decreased the proton affinity of carboxylic- and phenolic-type groups of HAs and FAs, and increased the heterogeneity of phenolic-type groups of HAs. As a whole, these effects indicated that the composting process could produce HA and FA fractions with greater cation binding capacities. These results suggest that composting of organic materials improves their agronomic and environmental value by increasing their potential to retain and exchange macro- and micronutrients, and to reduce the bioavailability of organic and inorganic pollutants.

  16. Eight salts constructed from 4-phenylthiazol-2-amine and carboxylic acid derivatives through combination of strong hydrogen bonding and weak noncovalent interactions

    NASA Astrophysics Data System (ADS)

    Jin, Shouwen; Zhu, Qiaowang; Wei, ShuaiShuai; Wang, Daqi

    2013-10-01

    Eight crystalline organic salts derived from 4-phenylthiazol-2-amine and carboxylic acid derivatives (2-chloronicotinic acid, 3-hydroxy-2-naphthoic acid, p-nitrobenzoic acid, 2-hydroxy-5-(phenyldiazenyl)benzoic acid, 5-nitrosalicylic acid, 5-sulfosalicylic acid, oxalic acid, and L-malic acid) were prepared and characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. In all of the salts except 6, 7, and 8, the 4-phenylthiazol-2-amine and carboxylic acid components are held together by two fused heterosynthons: a R22(7) heterosynthon and a R22(8) heterosynthon. All supramolecular architectures of the organic salts 1-8 involve extensive Nsbnd H⋯O hydrogen bonds as well as other noncovalent interactions. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. The salts displayed 2D/3D framework structure under these weak interactions.

  17. Sugar-Based Polyamides: Self-Organization in Strong Polar Organic Solvents.

    PubMed

    Rosu, Cornelia; Russo, Paul S; Daly, William H; Cueto, Rafael; Pople, John A; Laine, Roger A; Negulescu, Ioan I

    2015-09-14

    Periodic patterns resembling spirals were observed to form spontaneously upon unassisted cooling of d-glucaric acid- and d-galactaric acid-based polyamide solutions in N-methyl-N-morpholine oxide (NMMO) monohydrate. Similar observations were made in d-galactaric acid-based polyamide/ionic liquid (IL) solutions. The morphologies were investigated by optical, polarized light and confocal microscopy assays to reveal pattern details. Differential scanning calorimetry was used to monitor solution thermal behavior. Small- and wide-angle X-ray scattering data reflected the complex and heterogeneous nature of the self-organized patterns. Factors such as concentration and temperature were found to influence spiral dimensions and geometry. The distance between rings followed a first-order exponential decay as a function of polymer concentration. Fourier-Transform Infrared Microspectroscopy analysis of spirals pointed to H-bonding between the solvent and the pendant hydroxyl groups of the glucose units from the polymer backbone. Tests on self-organization into spirals of ketal-protected d-galactaric acid polyamides in NMMO monohydrate confirmed the importance of the monosaccharide's pendant free hydroxyl groups on the formation of these patterns. Rheology performed on d-galactaric-based polyamides at high concentration in NMMO monohydrate solution revealed the optimum conditions necessary to process these materials as fibers by spinning. The self-organization of these sugar-based polyamides mimics certain biological materials.

  18. Analytic calculation of physiological acid-base parameters in plasma.

    PubMed

    Wooten, E W

    1999-01-01

    Analytic expressions for plasma total titratable base, base excess (DeltaCB), strong-ion difference, change in strong-ion difference (DeltaSID), change in Van Slyke standard bicarbonate (DeltaVSSB), anion gap, and change in anion gap are derived as a function of pH, total buffer ion concentration, and conditional molar equilibrium constants. The behavior of these various parameters under respiratory and metabolic acid-base disturbances for constant and variable buffer ion concentrations is considered. For constant noncarbonate buffer concentrations, DeltaSID = DeltaCB = DeltaVSSB, whereas these equalities no longer hold under changes in noncarbonate buffer concentration. The equivalence is restored if the reference state is changed to include the new buffer concentrations.

  19. String-theory-based predictions for nonhydrodynamic collective modes in strongly interacting Fermi gases

    NASA Astrophysics Data System (ADS)

    Bantilan, H.; Brewer, J. T.; Ishii, T.; Lewis, W. E.; Romatschke, P.

    2016-09-01

    Very different strongly interacting quantum systems such as Fermi gases, quark-gluon plasmas formed in high-energy ion collisions, and black holes studied theoretically in string theory are known to exhibit quantitatively similar damping of hydrodynamic modes. It is not known if such similarities extend beyond the hydrodynamic limit. Do nonhydrodynamic collective modes in Fermi gases with strong interactions also match those from string theory calculations? In order to answer this question, we use calculations based on string theory to make predictions for modes outside the hydrodynamic regime in trapped Fermi gases. These predictions are amenable to direct testing with current state-of-the-art cold atom experiments.

  20. Strong coupling and polariton lasing in Te based microcavities embedding (Cd,Zn)Te quantum wells

    SciTech Connect

    Rousset, J.-G. Piętka, B.; Król, M.; Mirek, R.; Lekenta, K.; Szczytko, J.; Borysiuk, J.; Suffczyński, J.; Kazimierczuk, T.; Goryca, M.; Smoleński, T.; Kossacki, P.; Nawrocki, M.; Pacuski, W.

    2015-11-16

    We report on properties of an optical microcavity based on (Cd,Zn,Mg)Te layers and embedding (Cd,Zn)Te quantum wells. The key point of the structure design is the lattice matching of the whole structure to MgTe, which eliminates the internal strain and allows one to embed an arbitrary number of unstrained quantum wells in the microcavity. We evidence the strong light-matter coupling regime already for the structure containing a single quantum well. Embedding four unstrained quantum wells results in further enhancement of the exciton-photon coupling and the polariton lasing in the strong coupling regime.

  1. Separation of Acids, Bases, and Neutral Compounds

    NASA Astrophysics Data System (ADS)

    Fujita, Megumi; Mah, Helen M.; Sgarbi, Paulo W. M.; Lall, Manjinder S.; Ly, Tai Wei; Browne, Lois M.

    2003-01-01

    Separation of Acids, Bases, and Neutral Compounds requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime plug-in, version compatible with your OS and browser (available from MDL); and Flash player, version 5 or higher (available from Macromedia).

  2. Jigsaw Cooperative Learning: Acid-Base Theories

    ERIC Educational Resources Information Center

    Tarhan, Leman; Sesen, Burcin Acar

    2012-01-01

    This study focused on investigating the effectiveness of jigsaw cooperative learning instruction on first-year undergraduates' understanding of acid-base theories. Undergraduates' opinions about jigsaw cooperative learning instruction were also investigated. The participants of this study were 38 first-year undergraduates in chemistry education…

  3. The Magic Sign: Acids, Bases, and Indicators.

    ERIC Educational Resources Information Center

    Phillips, Donald B.

    1986-01-01

    Presents an approach that is used to introduce elementary and junior high students to a series of activities that will provide concrete experiences with acids, bases, and indicators. Provides instructions and listings of needed solutions and materials for developing this "magic sign" device. Includes background information and several student…

  4. Student Concept Changes in Acids and Bases.

    ERIC Educational Resources Information Center

    Ye, Renmin; Wells, Raymond R.

    This study focuses on student concept changes in acids and bases. Variables include field dependent level, personal independence level, interest in science or chemistry, teaching strategy, and student gender. This study of Grade 10 students (N=81) provides information relevant to secondary school chemistry learning, teaching, and concept change.…

  5. A new 5-lipoxygenase selective inhibitor derived from Artocarpus communis strongly inhibits arachidonic acid-induced ear edema.

    PubMed

    Koshihara, Y; Fujimoto, Y; Inoue, H

    1988-06-01

    Natural compounds isolated from the Indonesian plant, Artocarpus communis, inhibit 5-lipoxygenase of cultured mastocytoma cells. One of five compounds, AC-5-1, strongly inhibits 5-lipoxygenase with a half-inhibition dose of 5 +/- 0.12 X 10(-8) M. However, prostaglandin synthesizing activity is not inhibited until 10(-5) M. AC-5-1 is a highly selective inhibitor for 5-lipoxygenase. The AC-5-1 at 10(-5) M inhibits 96% of leukotriene C4 synthesis of mouse peritoneal cells facilitated by calcium-ionophore. Arachidonic acid-induced ear edema of mice, an in vivo inflammatory model, involving leukotriene induction, is strongly inhibited by AC-5-1 in a dose-dependent manner. The inhibition is the strongest of any inhibitors of 5-lipoxygenase reported previously. Since the natural compound AC-5-1 can selectively inhibit 5-lipoxygenase and affect in vivo inflammation, it will be interesting to investigate the role of leukotrienes on inflammation and other physiological processes.

  6. Drug-induced acid-base disorders.

    PubMed

    Kitterer, Daniel; Schwab, Matthias; Alscher, M Dominik; Braun, Niko; Latus, Joerg

    2015-09-01

    The incidence of acid-base disorders (ABDs) is high, especially in hospitalized patients. ABDs are often indicators for severe systemic disorders. In everyday clinical practice, analysis of ABDs must be performed in a standardized manner. Highly sensitive diagnostic tools to distinguish the various ABDs include the anion gap and the serum osmolar gap. Drug-induced ABDs can be classified into five different categories in terms of their pathophysiology: (1) metabolic acidosis caused by acid overload, which may occur through accumulation of acids by endogenous (e.g., lactic acidosis by biguanides, propofol-related syndrome) or exogenous (e.g., glycol-dependant drugs, such as diazepam or salicylates) mechanisms or by decreased renal acid excretion (e.g., distal renal tubular acidosis by amphotericin B, nonsteroidal anti-inflammatory drugs, vitamin D); (2) base loss: proximal renal tubular acidosis by drugs (e.g., ifosfamide, aminoglycosides, carbonic anhydrase inhibitors, antiretrovirals, oxaliplatin or cisplatin) in the context of Fanconi syndrome; (3) alkalosis resulting from acid and/or chloride loss by renal (e.g., diuretics, penicillins, aminoglycosides) or extrarenal (e.g., laxative drugs) mechanisms; (4) exogenous bicarbonate loads: milk-alkali syndrome, overshoot alkalosis after bicarbonate therapy or citrate administration; and (5) respiratory acidosis or alkalosis resulting from drug-induced depression of the respiratory center or neuromuscular impairment (e.g., anesthetics, sedatives) or hyperventilation (e.g., salicylates, epinephrine, nicotine).

  7. α,β-D-Constrained Nucleic Acids Are Strong Terminators of Thermostable DNA Polymerases in Polymerase Chain Reaction

    PubMed Central

    Mahéo, Sabrina; Gross, Grégori; Bodin, Pierre; Teissié, Justin; Escudier, Jean-Marc; Paquereau, Laurent

    2011-01-01

    (SC5′, RP) α,β-D- Constrained Nucleic Acids (CNA) are dinucleotide building blocks that can feature either B-type torsional angle values or non-canonical values, depending on their 5′C and P absolute stereochemistry. These CNA are modified neither on the nucleobase nor on the sugar structure and therefore represent a new class of nucleotide with specific chemical and structural characteristics. They promote marked bending in a single stranded DNA so as to preorganize it into a loop-like structure, and they have been shown to induce rigidity within oligonucleotides. Following their synthesis, studies performed on CNA have only focused on the constraints that this family of nucleotides introduced into DNA. On the assumption that bending in a DNA template may produce a terminator structure, we investigated whether CNA could be used as a new strong terminator of polymerization in PCR. We therefore assessed the efficiency of CNA as a terminator in PCR, using triethylene glycol phosphate units as a control. Analyses were performed by denaturing gel electrophoresis and several PCR products were further analysed by sequencing. The results showed that the incorporation of only one CNA was always skipped by the polymerases tested. On the other hand, two CNA units always stopped proofreading polymerases, such as Pfu DNA polymerase, as expected for a strong replication terminator. Non-proofreading enzymes, e.g. Taq DNA polymerase, did not recognize this modification as a strong terminator although it was predominantly stopped by this structure. In conclusion, this first functional use of CNA units shows that these modified nucleotides can be used as novel polymerization terminators of proofreading polymerases. Furthermore, our results lead us to propose that CNA and their derivatives could be useful tools for investigating the behaviour of different classes of polymerases. PMID:21991314

  8. Polarization shift keying based relay-assisted free space optical communication over strong turbulence with misalignment

    NASA Astrophysics Data System (ADS)

    Prabu, K.; Sriram Kumar, D.

    2016-01-01

    This paper investigates the outage performance of polarization shift keying (PolSK) based multihop parallel relay assisted free space optics (FSO) system over a strong atmospheric turbulence channel with misalignment fading. An exact closed form expression is derived for the end-to-end outage probability of the system. The results are compared with the direct transmission and on-off keying (OOK) based FSO systems. The results indicate that the performance of the PolSK based relay-assisted FSO system is much better than the direct transmission and OOK systems. The outage performance is enhanced by increasing the number of relay path between the transmitter and receiver.

  9. Strong and Long-Lasting Antinociceptive and Anti-inflammatory Conjugate of Naturally Occurring Oleanolic Acid and Aspirin

    PubMed Central

    Bednarczyk-Cwynar, Barbara; Wachowiak, Natalia; Szulc, Michal; Kamińska, Ewa; Bogacz, Anna; Bartkowiak-Wieczorek, Joanna; Zaprutko, Lucjusz; Mikolajczak, Przemyslaw L.

    2016-01-01

    The conjugate 8 was obtained as a result of condensation of 3-hydroxyiminooleanolic acid morfolide (7) and aspirin in dioxane. Analgesic effect of OAO-ASA (8) for the range of doses 0.3–300.0 mg/kg (p.o.) was performed in mice using a hot-plate test. Anti-inflammatory activity was assessed on carrageenan-induced paw edema in rats for the same range of doses. The conjugate OAO-ASA (8) did not significantly change locomotor activity of mice, therefore sedative properties of the compound should be excluded. The compound 8 proved a simple, proportional, dose-dependent analgesic action and expressed strong anti-inflammatory activity showing a reversed U-shaped, dose-dependent relation with its maximum at 30.0 mg/kg. After its combined administration with morphine (MF, 5.0 mg/kg, s.c.) the lowering of antinociceptive activity was found; however, the interaction with naloxone (NL, 3.0 mg/kg, s.c.) did not affect the antinociceptive effect of OAO-ASA (8), therefore its opioid mechanism of action should be rather excluded. After combined administration with acetylsalicylic acid (ASA, 300.0 mg/kg, p.o.) in hot-plate test, the examined compound 8 enhanced the antinociceptive activity in significant way. It also shows that rather the whole molecule is responsible for the antinociceptive and anti-inflammatory effect of the tested compound 8, however, it cannot be excluded that the summarizing effect is produced by ASA released from the compound 8 and the rest of triterpene derivative. The occurrence of tolerance for triterpenic derivative 8 was not observed, since the analgesic and anti-inflammatory effects after chronic administration of the conjugate OAO-ASA (8) was on the same level as after its single treatment. It seemed that the anti-inflammatory mechanism of action of OAO-ASA (8) is not simple, even its chronic administration lowered both blood concentration of IL-6 and mRNA IL-6 expression. However, the effects of the conjugate OAO-ASA (8) on TNF-α level and m

  10. Cationic Lipid-Based Nucleic Acid Vectors.

    PubMed

    Jubeli, Emile; Goldring, William P D; Pungente, Michael D

    2016-01-01

    The delivery of nucleic acids into cells remains an important laboratory cell culture technique and potential clinical therapy, based upon the initial cellular uptake, then translation into protein (in the case of DNA), or gene deletion by RNA interference (RNAi). Although viral delivery vectors are more efficient, the high production costs, limited cargo capacity, and the potential for clinical adverse events make nonviral strategies attractive. Cationic lipids are the most widely applied and studied nonviral vectors; however, much remains to be solved to overcome limitations of these systems. Advances in the field of cationic lipid-based nucleic acid (lipoplex) delivery rely upon the development of robust and reproducible lipoplex formulations, together with the use of cell culture assays. This chapter provides detailed protocols towards the formulation, delivery, and assessment of in vitro cationic lipid-based delivery of DNA. PMID:27436310

  11. Antifouling gold surfaces grafted with aspartic acid and glutamic acid based zwitterionic polymer brushes.

    PubMed

    Li, Wenchen; Liu, Qingsheng; Liu, Lingyun

    2014-10-28

    We report two new amino acid based antifouling zwitterionic polymers, poly(N(4)-(2-methacrylamidoethyl)asparagine) (pAspAA) and poly(N(5)-(2-methacrylamidoethyl)glutamine) (pGluAA). The vinyl monomers were developed from aspartic acid and glutamic acid. Surface-initiated photoiniferter-mediated polymerization was employed to graft polymer brushes from gold surfaces. Different thickness of polymer brushes was controlled by varying UV irradiation time. The nonspecific adsorption from undiluted human blood serum and plasma was studied by surface plasmon resonance (SPR). With the polymer film as thin as 11-12 nm, the adsorption on pAspAA from serum and plasma was as low as 0.75 and 5.18 ng/cm(2), respectively, and 1.88 and 10.15 ng/cm(2), respectively, for pGluAA. The adsorption amount is comparable to or even better than other amino acid based zwitterionic polymers such as poly(serine methacrylate), poly(lysine methacrylamide), and poly(ornithine methacrylamide) and other widely used antifouling polymers such as poly(sulfobetaine methacrylate), even under thinner polymer film thickness. The pAspAA and pGluAA grafted surfaces also showed strong resistance to endothelial cell attachment. The possession of both zwitterionic structure and hydrophilic amide groups, biomimetic property, and multifunctionality make pAspAA and pGluAA promising candidates for biocompatible antifouling functionalizable materials. PMID:25262768

  12. Antifouling gold surfaces grafted with aspartic acid and glutamic acid based zwitterionic polymer brushes.

    PubMed

    Li, Wenchen; Liu, Qingsheng; Liu, Lingyun

    2014-10-28

    We report two new amino acid based antifouling zwitterionic polymers, poly(N(4)-(2-methacrylamidoethyl)asparagine) (pAspAA) and poly(N(5)-(2-methacrylamidoethyl)glutamine) (pGluAA). The vinyl monomers were developed from aspartic acid and glutamic acid. Surface-initiated photoiniferter-mediated polymerization was employed to graft polymer brushes from gold surfaces. Different thickness of polymer brushes was controlled by varying UV irradiation time. The nonspecific adsorption from undiluted human blood serum and plasma was studied by surface plasmon resonance (SPR). With the polymer film as thin as 11-12 nm, the adsorption on pAspAA from serum and plasma was as low as 0.75 and 5.18 ng/cm(2), respectively, and 1.88 and 10.15 ng/cm(2), respectively, for pGluAA. The adsorption amount is comparable to or even better than other amino acid based zwitterionic polymers such as poly(serine methacrylate), poly(lysine methacrylamide), and poly(ornithine methacrylamide) and other widely used antifouling polymers such as poly(sulfobetaine methacrylate), even under thinner polymer film thickness. The pAspAA and pGluAA grafted surfaces also showed strong resistance to endothelial cell attachment. The possession of both zwitterionic structure and hydrophilic amide groups, biomimetic property, and multifunctionality make pAspAA and pGluAA promising candidates for biocompatible antifouling functionalizable materials.

  13. Acid-Base Balance in Uremic Rats with Vascular Calcification

    PubMed Central

    Peralta-Ramírez, Alan; Raya, Ana Isabel; Pineda, Carmen; Rodríguez, Mariano; Aguilera-Tejero, Escolástico; López, Ignacio

    2014-01-01

    Background/Aims Vascular calcification (VC), a major complication in humans and animals with chronic kidney disease (CKD), is influenced by changes in acid-base balance. The purpose of this study was to describe the acid-base balance in uremic rats with VC and to correlate the parameters that define acid-base equilibrium with VC. Methods Twenty-two rats with CKD induced by 5/6 nephrectomy (5/6 Nx) and 10 nonuremic control rats were studied. Results The 5/6 Nx rats showed extensive VC as evidenced by a high aortic calcium (9.2 ± 1.7 mg/g of tissue) and phosphorus (20.6 ± 4.9 mg/g of tissue) content. Uremic rats had an increased pH level (7.57 ± 0.03) as a consequence of both respiratory (PaCO2 = 28.4 ± 2.1 mm Hg) and, to a lesser degree, metabolic (base excess = 4.1 ± 1 mmol/l) derangements. A high positive correlation between both anion gap (AG) and strong ion difference (SID) with aortic calcium (AG: r = 0.604, p = 0.02; SID: r = 0.647, p = 0.01) and with aortic phosphorus (AG: r = 0.684, p = 0.007; SID: r = 0.785, p = 0.01) was detected. Conclusions In an experimental model of uremic rats, VC showed high positive correlation with AG and SID. PMID:25177336

  14. Estimation of the occurrence rate of strong earthquakes based on hidden semi-Markov models

    NASA Astrophysics Data System (ADS)

    Votsi, I.; Limnios, N.; Tsaklidis, G.; Papadimitriou, E.

    2012-04-01

    The present paper aims at the application of hidden semi-Markov models (HSMMs) in an attempt to reveal key features for the earthquake generation, associated with the actual stress field, which is not accessible to direct observation. The models generalize the hidden Markov models by considering the hidden process to form actually a semi-Markov chain. Considering that the states of the models correspond to levels of actual stress fields, the stress field level at the occurrence time of each strong event is revealed. The dataset concerns a well catalogued seismically active region incorporating a variety of tectonic styles. More specifically, the models are applied in Greece and its surrounding lands, concerning a complete data sample with strong (M≥ 6.5) earthquakes that occurred in the study area since 1845 up to present. The earthquakes that occurred are grouped according to their magnitudes and the cases of two and three magnitude ranges for a corresponding number of states are examined. The parameters of the HSMMs are estimated and their confidence intervals are calculated based on their asymptotic behavior. The rate of the earthquake occurrence is introduced through the proposed HSMMs and its maximum likelihood estimator is calculated. The asymptotic properties of the estimator are studied, including the uniformly strongly consistency and the asymptotical normality. The confidence interval for the proposed estimator is given. We assume the state space of both the observable and the hidden process to be finite, the hidden Markov chain to be homogeneous and stationary and the observations to be conditionally independent. The hidden states at the occurrence time of each strong event are revealed and the rate of occurrence of an anticipated earthquake is estimated on the basis of the proposed HSMMs. Moreover, the mean time for the first occurrence of a strong anticipated earthquake is estimated and its confidence interval is calculated.

  15. Chem I Supplement: Emphasis on Acids and Bases

    ERIC Educational Resources Information Center

    Journal of Chemical Education Staff

    1977-01-01

    Provides supplementary notes on acids and bases suitable for secondary school chemistry instruction, including acidity in solid and natural waters, acidity balance in body chemistry, acid and basic foods, pH values of common fluids, examples of drugs, and commercial preparation of nitric acid. (SL)

  16. Analysis of aqueous solutions by near-infrared spectrometry (NIRS). I. Titrations of strong acids with strong bases

    NASA Astrophysics Data System (ADS)

    Molt, K.; Cho, Y. J.

    1995-04-01

    The titration of 1 M HCl with 2 M NaOH was observed by NIR-spectrometry. The measured spectra can be evaluated quantitatively for calibration of the H +- and OH --concentration. The NIRS errors with respect to the prediction of the pH and the equivalence point are discussed.

  17. Buoyancy-driven instabilities of acid-base fronts

    NASA Astrophysics Data System (ADS)

    Almarcha, Christophe; R'honi, Yasmina; Trevelyan, Philip M. J.; de Wit, Anne

    2010-11-01

    Chemical reactions can produce buoyancy-driven motions in solutions by changing the local density in the gravity field. Starting from a stratification of one given miscible reactant solution on top of another miscible one, convective destabilization influenced by the reaction can emerge as a combination of several non-reactive hydrodynamic instabilities, including Rayleigh-Taylor and double diffusive instabilities. In the specific case of reactions between a strong acid and a strong base, we show that all the possible scenarios reduce to the composition of only two asymptotic situations because products generated at the reactive zone are always less dense and slower diffusing than the reactants. Experiments in a vertically orientated Hele-Shaw cell confirm the theoretical predictions and can be quantitatively compared to numerical simulations of a nonlinear reaction-diffusion-convection model.

  18. Separation of thorium and uranium in nitric acid solution using silica based anion exchange resin.

    PubMed

    Chen, Yanliang; Wei, Yuezhou; He, Linfeng; Tang, Fangdong

    2016-09-30

    To separate thorium and uranium in nitric acid solution using anion exchange process, a strong base silica-based anion exchange resin (SiPyR-N4) was synthesized. Batch experiments were conducted and the separation factor of thorium and uranium in 9M nitric acid was about 10. Ion exchange chromatography was applied to separate thorium and uranium in different ratios. Uranium could be eluted by 9M nitric acid and thorium was eluted by 0.1M nitric acid. It was proved that thorium and uranium can be separated and recovered successfully by this method.

  19. Separation of thorium and uranium in nitric acid solution using silica based anion exchange resin.

    PubMed

    Chen, Yanliang; Wei, Yuezhou; He, Linfeng; Tang, Fangdong

    2016-09-30

    To separate thorium and uranium in nitric acid solution using anion exchange process, a strong base silica-based anion exchange resin (SiPyR-N4) was synthesized. Batch experiments were conducted and the separation factor of thorium and uranium in 9M nitric acid was about 10. Ion exchange chromatography was applied to separate thorium and uranium in different ratios. Uranium could be eluted by 9M nitric acid and thorium was eluted by 0.1M nitric acid. It was proved that thorium and uranium can be separated and recovered successfully by this method. PMID:27614730

  20. A General Simulator for Acid-Base Titrations

    NASA Astrophysics Data System (ADS)

    de Levie, Robert

    1999-07-01

    General formal expressions are provided to facilitate the automatic computer calculation of acid-base titration curves of arbitrary mixtures of acids, bases, and salts, without and with activity corrections based on the Davies equation. Explicit relations are also given for the buffer strength of mixtures of acids, bases, and salts.

  1. C-H-Activated Direct Arylation of Strong Benzothiadiazole and Quinoxaline-Based Electron Acceptors.

    PubMed

    Zhang, Junxiang; Parker, Timothy C; Chen, Wayne; Williams, LaRita; Khrustalev, Victor N; Jucov, Evgheni V; Barlow, Stephen; Timofeeva, Tatiana V; Marder, Seth R

    2016-01-15

    Electron acceptors are important components of π-conjugated materials, but the strong electron-withdrawing properties of the required synthetic intermediates often make them poor substrates in synthetic schemes designed around conventional organometallic cross-coupling. Here, strong benzodiimine-based acceptors, including 5,6-difluoro[2,1,3]benzothiadiazole, 5,6-dicyano[2,1,3]benzothiadiazole, 5,6-dicyanobenzo[d][1,2,3]triazole, 6,7-dicyanoquinoxaline, and 6,7-dinitroquinoxaline, are shown to undergo facile palladium-catalyzed C-H direct arylation with a variety of bromoarenes in moderate to high yields. The electrochemical characteristics of di-2-thienyl derivatives synthesized using this methodology are compared and suggest that, in an electron-transfer sense, 5,6-dicyano[2,1,3]benzothiadiazole is a comparably strong acceptor to benzo[1,2-c:4,5-c']bis[1,2,5]thiadiazole. The synthetic results suggest that high electron-withdrawing ability, which has traditionally limited reaction yields and structural variety in organic electronic materials, may be advantageous when employing C-H activated direct arylation in certain circumstances.

  2. Designed microtremor array based actual measurement and analysis of strong ground motion at Palu city, Indonesia

    SciTech Connect

    Thein, Pyi Soe; Pramumijoyo, Subagyo; Wilopo, Wahyu; Setianto, Agung; Brotopuspito, Kirbani Sri; Kiyono, Junji; Putra, Rusnardi Rahmat

    2015-04-24

    In this study, we investigated the strong ground motion characteristics under Palu City, Indonesia. The shear wave velocity structures evaluated by eight microtremors measurement are the most applicable to determine the thickness of sediments and average shear wave velocity with Vs ≤ 300 m/s. Based on subsurface underground structure models identified, earthquake ground motion was estimated in the future Palu-Koro earthquake by using statistical green’s function method. The seismic microzonation parameters were carried out by considering several significant controlling factors on ground response at January 23, 2005 earthquake.

  3. pH-responsive ion transport in polyelectrolyte multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA) bearing strong- and weak anionic groups.

    PubMed

    Maza, Eliana; Tuninetti, Jimena S; Politakos, Nikolaos; Knoll, Wolfgang; Moya, Sergio; Azzaroni, Omar

    2015-11-28

    The layer-by-layer construction of interfacial architectures displaying stimuli-responsive control of mass transport is attracting increasing interest in materials science. In this work, we describe the creation of interfacial architectures displaying pH-dependent ionic transport properties which until now have not been observed in polyelectrolyte multilayers. We describe a novel approach to create pH-controlled ion-rectifying systems employing polyelectrolyte multilayers assembled from a copolymer containing both weakly and strongly charged pendant groups, poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA), alternately deposited with poly(diallyldimethylammonium chloride) (PDADMAC). The conceptual framework is based on the very contrasting and differential interactions of PSS and MA units with PDADMAC. In our setting, sulfonate groups play a structural role by conferring stability to the multilayer due to the strong electrostatic interactions with the polycations, while the weakly interacting MA groups remain "silent" within the film and then act as on-demand pH-responsive units. When these multilayers are combined with a strong cationic capping layer that repels the passage of cationic probes, a pH-gateable rectified transport of anions is observed. Concomitantly, we also observed that these functional properties are significantly affected when multilayers are subjected to extensive pH cycling as a consequence of irreversible morphological changes taking place in the film. We envision that the synergy derived from combining weak and strong interactions within the same multilayer will play a key role in the construction of new interfacial architectures displaying tailorable ion transport properties. PMID:26489595

  4. Structure of six organic acid-base adducts from 6-bromobenzo[d]thiazol-2-amine and acidic compounds

    NASA Astrophysics Data System (ADS)

    Jin, Shouwen; Zhang, Jing; Wang, Daqi; Tao, Lin; Zhou, Mengjian; Shen, Yinyan; Chen, Quan; Lin, Zhanghui; Gao, Xingjun

    2014-05-01

    Six anhydrous organic acid-base adducts of 6-bromobenzo[d]thiazol-2-amine were prepared with organic acids as 2,4,6-trinitrophenol, salicylic acid, 3,5-dinitrobenzoic acid, 3,5-dinitrosalicylic acid, malonic acid and sebacic acid. The compounds 1-6 were characterized by X-ray diffraction analysis, IR, and elemental analysis. The melting points of all the adducts were given. Of the six adducts, 1, 3, 4, and 5 are organic salts, while 2, and 6 are cocrystals. The supramolecular arrangement in the crystals 2-6 is based on the R22(8) synthon. Analysis of the crystal packing of 1-6 suggests that there are strong NH⋯O, OH⋯N, and OH⋯O hydrogen bonds (charge assisted or neutral) between acid and base components in the supramolecular assemblies. When the hydroxyl group is present in the ortho position of the carboxy, the intramolecular S6 synthon is present, as expected. Besides the classical hydrogen bonding interactions, other noncovalent interactions also play important roles in structure extension. Due to the synergetic effect of these weak interactions, compounds 1-6 display 1D-3D framework structure.

  5. Acid Base Equilibrium in a Lipid/Water Gel

    NASA Astrophysics Data System (ADS)

    Streb, Kristina K.; Ilich, Predrag-Peter

    2003-12-01

    A new and original experiment in which partition of bromophenol blue dye between water and lipid/water gel causes a shift in the acid base equilibrium of the dye is described. The dye-absorbing material is a monoglyceride food additive of plant origin that mixes freely with water to form a stable cubic phase gel; the nascent gel absorbs the dye from aqueous solution and converts it to the acidic form. There are three concurrent processes taking place in the experiment: (a) formation of the lipid/water gel, (b) absorption of the dye by the gel, and (c) protonation of the dye in the lipid/water gel environment. As the aqueous solution of the dye is a deep purple-blue color at neutral pH and yellow at acidic pH the result of these processes is visually striking: the strongly green-yellow particles of lipid/water gel are suspended in purple-blue aqueous solution. The local acidity of the lipid/water gel is estimated by UV vis spectrophotometry. This experiment is an example of host-guest (lipid/water gel dye) interaction and is suitable for project-type biophysics, physical chemistry, or biochemistry labs. The experiment requires three, 3-hour lab sessions, two of which must not be separated by more than two days.

  6. An Introductory Laboratory Exercise for Acids and Bases.

    ERIC Educational Resources Information Center

    Miller, Richard; Silberman, Robert

    1986-01-01

    Discusses an acid-base neutralization exercise requiring groups of students to determine: (1) combinations of solutions giving neutralization; (2) grouping solutions as acids or bases; and (3) ranking groups in order of concentration. (JM)

  7. The Bronsted-Lowery Acid-Base Concept.

    ERIC Educational Resources Information Center

    Kauffman, George B.

    1988-01-01

    Gives the background history of the simultaneous discovery of acid-base relationships by Johannes Bronsted and Thomas Lowry. Provides a brief biographical sketch of each. Discusses their concept of acids and bases in some detail. (CW)

  8. Coronavirus phylogeny based on triplets of nucleic acids bases

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Liu, Yanshu; Li, Renfa; Zhu, Wen

    2006-04-01

    We considered the fully overlapping triplets of nucleotide bases and proposed a 2D graphical representation of protein sequences consisting of 20 amino acids and a stop code. Based on this 2D graphical representation, we outlined a new approach to analyze the phylogenetic relationships of coronaviruses by constructing a covariance matrix. The evolutionary distances are obtained through measuring the differences among the two-dimensional curves.

  9. Mathematical modeling of acid-base physiology

    PubMed Central

    Occhipinti, Rossana; Boron, Walter F.

    2015-01-01

    pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3− , NH4+) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cell–which to our knowledge is the first one capable of handling a multitude of buffer reaction–that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3− influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis. PMID:25617697

  10. Mathematical modeling of acid-base physiology.

    PubMed

    Occhipinti, Rossana; Boron, Walter F

    2015-01-01

    pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3(-), [Formula: see text] ) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cells-which to our knowledge is the first one capable of handling a multitude of buffer reactions-that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3(-) influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis.

  11. Bipolar Membranes for Acid Base Flow Batteries

    NASA Astrophysics Data System (ADS)

    Anthamatten, Mitchell; Roddecha, Supacharee; Jorne, Jacob; Coughlan, Anna

    2011-03-01

    Rechargeable batteries can provide grid-scale electricity storage to match power generation with consumption and promote renewable energy sources. Flow batteries offer modular and flexible design, low cost per kWh and high efficiencies. A novel flow battery concept will be presented based on acid-base neutralization where protons (H+) and hydroxyl (OH-) ions react electrochemically to produce water. The large free energy of this highly reversible reaction can be stored chemically, and, upon discharge, can be harvested as usable electricity. The acid-base flow battery concept avoids the use of a sluggish oxygen electrode and utilizes the highly reversible hydrogen electrode, thus eliminating the need for expensive noble metal catalysts. The proposed flow battery is a hybrid of a battery and a fuel cell---hydrogen gas storing chemical energy is produced at one electrode and is immediately consumed at the other electrode. The two electrodes are exposed to low and high pH solutions, and these solutions are separated by a hybrid membrane containing a hybrid cation and anion exchange membrane (CEM/AEM). Membrane design will be discussed, along with ion-transport data for synthesized membranes.

  12. Quasiparticle cascade amplifier based on strong electron cooling of normal metal traps

    NASA Astrophysics Data System (ADS)

    Kuzmin, L.

    2002-08-01

    A novel concept of the quasiparticle amplifier based on the trapping of nonequilibrium quasiparticles, strong direct electron cooling, and the cascade principle of amplification has been suggested. The amplifier can be useful for the normal metal hot-electron bolometers (NHEB) with SIN tunnel junctions and similar devices. In the suggested concept, the second stage is working in a regime of strong direct electron cooling whereby all released energy is removed from the trap by the second tunnel junction. In this case, one can maintain the temperature of the trap near a base level while keeping a high coefficient of amplification. Another important feature of the proposed amplifier is adding the stimulated current I2 to the main measurement current I1 to increase amplification. In this regime, the coefficient of amplification will be greater than unity in any case. The junctions T1 and T2 (of a different area) work in opposite directions with the same voltage near Δ that can be realized only in voltage-biased mode. The principle of cascade amplification can be extended further for a third stage (and so on) with the same adding amplified currents from junctions of increased area. The cascade principle with the same voltage bias for all junctions gives an opportunity to realize an amplifier without an additional power supply and additional wires. This feature can be extremely important for the realization of the multi-pixel arrays of the sensors.

  13. Photoinduced strong acid–weak base reactions in a polar aprotic solvent

    NASA Astrophysics Data System (ADS)

    Lee, Young Min; Park, Sun-Young; Kim, Heesu; Gyum Kim, Taeg; Kwon, Oh-Hoon

    2016-06-01

    The excited-state proton transfer (ESPT) of the strong photoacid, N-methyl-7-hydroxyquinolinium, was studied in the presence of different weak bases such as methanol, ethanol, and dimethyl sulfoxide in an aprotic solvent of acetonitrile. Here, we present chemical kinetics analysis of the ESPT mechanism to explain biphasic fluorescence decay of the parent photoacid and the sign reversal of the rise and decay of the resulting conjugate-base fluorescence. The ESPT of the free photoacid showed a molecularity of 2 with reacting alcohol molecules. In the ground state, it was found that a fraction of the photoacid formed 1 : 2 hydrogen-bonded complexes with the residual water present in the aprotic solvent or 1 : 1 complexes with the additive alcohols. In the excited state, these adducts underwent proton transfer when complexed further with diffusing alcohol molecules.

  14. Teaching Acid/Base Physiology in the Laboratory

    ERIC Educational Resources Information Center

    Friis, Ulla G.; Plovsing, Ronni; Hansen, Klaus; Laursen, Bent G.; Wallstedt, Birgitta

    2010-01-01

    Acid/base homeostasis is one of the most difficult subdisciplines of physiology for medical students to master. A different approach, where theory and practice are linked, might help students develop a deeper understanding of acid/base homeostasis. We therefore set out to develop a laboratory exercise in acid/base physiology that would provide…

  15. Using Willie's Acid-Base Box for Blood Gas Analysis

    ERIC Educational Resources Information Center

    Dietz, John R.

    2011-01-01

    In this article, the author describes a method developed by Dr. William T. Lipscomb for teaching blood gas analysis of acid-base status and provides three examples using Willie's acid-base box. Willie's acid-base box is constructed using three of the parameters of standard arterial blood gas analysis: (1) pH; (2) bicarbonate; and (3) CO[subscript…

  16. [Practical diagnostics of acid-base disorders: part I: differentiation between respiratory and metabolic disturbances].

    PubMed

    Deetjen, P; Lichtwarck-Aschoff, M

    2012-11-01

    The first part of this overview on diagnostic tools for acid-base disorders focuses on basic knowledge for distinguishing between respiratory and metabolic causes of a particular disturbance. Rather than taking sides in the great transatlantic or traditional-modern debate on the best theoretical model for understanding acid-base physiology, this article tries to extract what is most relevant for everyday clinical practice from the three schools involved in these keen debates: the Copenhagen, the Boston and the Stewart schools. Each school is particularly strong in a specific diagnostic or therapeutic field. Appreciating these various strengths a unifying, simplified algorithm together with an acid-base calculator will be discussed.

  17. [Progress in biotransformation of bio-based lactic acid ].

    PubMed

    Gao, Chao; Ma, Cuiqing; Xu, Ping

    2013-10-01

    Fermentative production of lactic acid, an important bio-based chemicals, has made considerable progress. In addition to the food industry and production of polylactic acid, lactic acid also can be used as an important platform chemical for the production of acrylic acid, pyruvic acid, 1,2-propanediol, and lactic acid esters. This article summarizes the recent progress in biocatalytic production of lactic acid derivatives by dehydration, dehydrogenation, reduction, and esterification. Trends in the biotransformation of lactic acid are also discussed. PMID:24432656

  18. Ambient cure polyimide foams prepared from aromatic polyisocyanates, aromatic polycarboxylic compounds, furfuryl alcohol, and a strong inorganic acid

    NASA Technical Reports Server (NTRS)

    Sawko, Paul M. (Inventor); Riccitiello, Salvatore R. (Inventor); Hamermesh, Charles L. (Inventor)

    1980-01-01

    Flame and temperature resistant polyimide foams are prepared by the reaction of an aromatic dianhydride, e.g., pyromellitic dianhydride, with an aromatic polyisocyanate, e.g., polymethylene polyphenylisocyanate (PAPI) in the presence of an inorganic acid and a lower molecular weight alcohol, e.g., dilute sulfuric acid or phosphoric acid and furfuryl alcohol. The exothermic reaction between the acid and the alcohol provides the heat necessary for the other reactants to polymerize without the application of any external heat. Such mixtures, therefore, are ideally suited for in situ foam formation, especially where the application of heat is not practical or possible.

  19. Fermi surface nesting induced strong pairing in iron-based superconductors

    PubMed Central

    Terashima, K.; Sekiba, Y.; Bowen, J. H.; Nakayama, K.; Kawahara, T.; Sato, T.; Richard, P.; Xu, Y.-M.; Li, L. J.; Cao, G. H.; Xu, Z.-A.; Ding, H.; Takahashi, T.

    2009-01-01

    The discovery of high-temperature superconductivity in iron pnictides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation of Fermi-surface (FS)-dependent nodeless superconducting gaps suggested that inter-FS interactions may play a crucial role in superconducting pairing. In the optimally hole-doped Ba0.6K0.4Fe2As2, the pairing strength is enhanced simultaneously (2Δ/Tc≈7) on the nearly nested FS pockets, i.e., the inner hole-like (α) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Δ/Tc≈3.6) in the poorly nested outer hole-like (β) FS. Here, we report that in the electron-doped BaFe1.85Co0.15As2, the FS nesting condition switches from the α to the β FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Δ/Tc≈6) is also found to switch to the nested β FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors. PMID:19359490

  20. Biomass-Based Mechanically Strong and Electrically Conductive Polymer Aerogels and Their Application for Supercapacitors.

    PubMed

    Zhao, Hai-Bo; Yuan, Lei; Fu, Zhi-Bing; Wang, Chao-Yang; Yang, Xi; Zhu, Jia-Yi; Qu, Jing; Chen, Hong-Bing; Schiraldi, David A

    2016-04-20

    A novel biomass-based mechanically strong and electrically conductive polymer aerogel was fabricated from aniline and biodegradable pectin. The strong hydrogen bonding interactions between polyaniline (PANI) and pectin resulted in a defined structure and enhanced properties of the aerogel. All the resultant aerogels exhibited self-surppoted 3D nanoporous network structures with high surface areas (207-331m(2)/g) and hierarchical pores. The results from electrical conductivity measurements and compressive tests revealed that these aerogels also had favorable conductivities (0.002-0.1 S/m) and good compressive modulus (1.2-1.4 MPa). The aerogel further used as electrode for supercapacitors showed enhanced capacitive performance (184 F/g at 0.5 A/g). Over 74% of the initial capacitance was maintained after repeating 1000 cycles of the cylic voltammetry test, while the capacitance retention of PANI was only 57%. The improved electrochemical performance may be attributed to the combinative properties of good electrical conductivity, BET surface areas, and stable nanoporous structure of the aerogel. Thus, this aerogel shows great potential as electrode materials for supercapacitors. PMID:27045343

  1. Hemolymph acid-base balance of the crayfish Astacus leptodactylus as a function of the oxygenation and the acid-base balance of the ambient water.

    PubMed

    Dejours, P; Armand, J

    1980-07-01

    The acid-base balance of the prebranchial hemolymph of the crayfish Astacus leptodactylus was studied at various acid-base balances and levels of oxygenation of the ambient water at 13 degrees C. The water acid-base balance was controlled automatically by a pH-CO2-stat. Into water of constant titration alkalinity, TA, this device intermittenly injects carbon dioxide to maintain the pH at a preset value. Water pH was reduced to the same value either by hypercapnia (at constant TA) or by adding HCl or H2SO4 to decrease the TA (at constant CO2 tension). Decrease of hemolymph pH and increase of hemolymph PCO2 were similar for the three acidic waters. Water oxygenation changes strongly affected hemolymph ABB. In crayfish living in hyperoxic water (PO2 congruent to 600 Torr) compared to those in hypoxic water (PO2 congruent to 40 Torr), hemolymph pH was 0.3 to 0.4 unit lower and hemolymph PCO2 several times higher, the exact values of pH and PCO2 depending on the controlled ambient acid-base balance. In any study of the hemolymph acid-base balance of the crayfish, it is an important to control ambient water's acid-base balance and oxygenation as it is to control its temperature, a conclusion which probably holds true for studies on all water breathers.

  2. Identifying a base in a nucleic acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    2005-02-08

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  3. Online sensor fault detection based on an improved strong tracking filter.

    PubMed

    Wang, Lijuan; Wu, Lifeng; Guan, Yong; Wang, Guohui

    2015-01-01

    We propose a method for online sensor fault detection that is based on the evolving Strong Tracking Filter (STCKF). The cubature rule is used to estimate states to improve the accuracy of making estimates in a nonlinear case. A residual is the difference in value between an estimated value and the true value. A residual will be regarded as a signal that includes fault information. The threshold is set at a reasonable level, and will be compared with residuals to determine whether or not the sensor is faulty. The proposed method requires only a nominal plant model and uses STCKF to estimate the original state vector. The effectiveness of the algorithm is verified by simulation on a drum-boiler model. PMID:25690553

  4. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-07-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis.

  5. Paramagnetic molecule induced strong antiferromagnetic exchange coupling on a magnetic tunnel junction based molecular spintronics device.

    PubMed

    Tyagi, Pawan; Baker, Collin; D'Angelo, Christopher

    2015-07-31

    This paper reports our Monte Carlo (MC) studies aiming to explain the experimentally observed paramagnetic molecule induced antiferromagnetic coupling between ferromagnetic (FM) electrodes. Recently developed magnetic tunnel junction based molecular spintronics devices (MTJMSDs) were prepared by chemically bonding the paramagnetic molecules between the FM electrodes along the tunnel junction's perimeter. These MTJMSDs exhibited molecule-induced strong antiferromagnetic coupling. We simulated the 3D atomic model analogous to the MTJMSD and studied the effect of molecule's magnetic couplings with the two FM electrodes. Simulations show that when a molecule established ferromagnetic coupling with one electrode and antiferromagnetic coupling with the other electrode, then theoretical results effectively explained the experimental findings. Our studies suggest that in order to align MTJMSDs' electrodes antiparallel to each other, the exchange coupling strength between a molecule and FM electrodes should be ∼50% of the interatomic exchange coupling for the FM electrodes.

  6. Online Sensor Fault Detection Based on an Improved Strong Tracking Filter

    PubMed Central

    Wang, Lijuan; Wu, Lifeng; Guan, Yong; Wang, Guohui

    2015-01-01

    We propose a method for online sensor fault detection that is based on the evolving Strong Tracking Filter (STCKF). The cubature rule is used to estimate states to improve the accuracy of making estimates in a nonlinear case. A residual is the difference in value between an estimated value and the true value. A residual will be regarded as a signal that includes fault information. The threshold is set at a reasonable level, and will be compared with residuals to determine whether or not the sensor is faulty. The proposed method requires only a nominal plant model and uses STCKF to estimate the original state vector. The effectiveness of the algorithm is verified by simulation on a drum-boiler model. PMID:25690553

  7. Periodic Forcing of a 555-IC Based Electronic Oscillator in the Strong Coupling Limit

    NASA Astrophysics Data System (ADS)

    Santillán, Moisés

    We designed and developed a master-slave electronic oscillatory system (based on the 555-timer IC working in the astable mode), and investigated its dynamic behavior regarding synchronization. For that purpose, we measured the rotation numbers corresponding to the phase-locking rhythms achieved in a large set of values of the normalized forcing frequency (NFF) and of the coupling strength between the master and the slave oscillators. In particular, we were interested in the system behavior in the strong-coupling limit, because such problem has not been extensively studied from an experimental perspective. Our results indicate that, in such a limit, a degenerate codimension-2 bifurcation point at NFF = 2 exists, in which all the phase-locking regions converge. These findings were corroborated by means of a mathematical model developed to that end, as well as by ad hoc further experiments.

  8. Wave-based control of under-actuated flexible structures with strong external disturbing forces

    NASA Astrophysics Data System (ADS)

    O'Connor, William J.; Habibi, Hossein

    2015-09-01

    Wave-based control of under-actuated, flexible systems has many advantages over other methods. It considers actuator motion as launching a mechanical wave into the flexible system which it absorbs on its return to the actuator. The launching and absorbing proceed simultaneously. This simple, intuitive idea leads to robust, generic, highly efficient, precise, adaptable controllers, allowing rapid and almost vibrationless re-positioning of the system, using only sensors collocated at the actuator-system interface. It has been very successfully applied to simple systems such as mass-spring strings, systems of Euler-Bernoulli beams, planar mass-spring arrays, and flexible three-dimensional space structures undergoing slewing motion. In common with most other approaches, this work also assumed that, during a change of position, the forces from the environment were negligible in comparison with internal forces and torques. This assumption is not always valid. Strong external forces considerably complicate the flexible control problem, especially when unknown, unexpected or unmodelled. The current work extends the wave-based strategy to systems experiencing significant external disturbing forces, whether enduring or transient. The work also provides further robustness to sensor errors. The strategy has the controller learn about the disturbances and compensate for them, yet without needing new sensors, measurements or models beyond those of standard wave-based control.

  9. Impact of the diet on net endogenous acid production and acid-base balance.

    PubMed

    Poupin, Nathalie; Calvez, Juliane; Lassale, Camille; Chesneau, Caroline; Tomé, Daniel

    2012-06-01

    Net acid production, which is composed of volatile acids (15,000 mEq/day) and metabolic acids (70-100 mEq/day) is relatively small compared to whole-body H⁺ turnover (150,000 mEq/day). Metabolic acids are ingested from the diet or produced as intermediary or end products of endogenous metabolism. The three commonly reported sources of net acid production are the metabolism of sulphur amino acids, the metabolism or ingestion of organic acids, and the metabolism of phosphate esters or dietary phosphoproteins. Net base production occurs mainly as a result of absorption of organic anions from the diet. To maintain acid-base balance, ingested and endogenously produced acids are neutralized within the body by buffer systems or eliminated from the body through the respiratory (excretion of volatile acid in the form of CO₂) and urinary (excretion of fixed acids and remaining H⁺) pathways. Because of the many reactions involved in the acid-base balance, the direct determination of acid production is complex and is usually estimated through direct or indirect measurements of acid excretion. However, indirect approaches, which assess the acid-forming potential of the ingested diet based on its composition, do not take all the acid-producing reactions into account. Direct measurements therefore seem more reliable. Nevertheless, acid excretion does not truly provide information on the way acidity is dealt with in the plasma and this measurement should be interpreted with caution when assessing acid-base imbalance.

  10. Metal amides as the simplest acid/base catalysts for stereoselective carbon-carbon bond-forming reactions.

    PubMed

    Yamashita, Yasuhiro; Kobayashi, Shū

    2013-07-15

    In this paper, new possibilities for metal amides are described. Although typical metal amides are recognized as strong stoichiometric bases for deprotonation of inert or less acidic hydrogen atoms, transition-metal amides, namely silver and copper amides, show interesting abilities as one of the simplest acid/base catalysts in stereoselective carbon-carbon bond-forming reactions.

  11. Polymer gel dosimeter based on itaconic acid.

    PubMed

    Mattea, Facundo; Chacón, David; Vedelago, José; Valente, Mauro; Strumia, Miriam C

    2015-11-01

    A new polymeric dosimeter based on itaconic acid and N, N'-methylenebisacrylamide was studied. The preparation method, compositions of monomer and crosslinking agent and the presence of oxygen in the dosimetric system were analyzed. The resulting materials were irradiated with an X-ray tube at 158cGy/min, 226cGymin and 298cGy/min with doses up to 1000Gy. The dosimeters presented a linear response in the dose range 75-1000Gy, sensitivities of 0.037 1/Gyat 298cGy/min and an increase in the sensitivity with lower dose rates. One of the most relevant outcomes in this study was obtaining different monomer to crosslinker inclusion in the formed gel for the dosimeters where oxygen was purged during the preparation method. This effect has not been reported in other typical dosimeters and could be attributed to the large differences in the reactivity among these species.

  12. Persistent Scatterer Interferometry based detection of strong subsidence in Semarang, Indonesia

    NASA Astrophysics Data System (ADS)

    Cahyadi Kalia, Andre

    2016-04-01

    The City of Semarang (Indonesia) faces land subsidence since more than 100 years. The impact for the cities approximately 1.3 million inhabitants is severe: strong subsidence (up to several cm per year) affect the living environment, buildings and infrastructure. The main reasons for the subsidence is groundwater extraction, compaction of coastal sediments and construction load. In order to monitor the spatio-temporal variability of the subsidence phenomena the Persistent Scatterer Interferometry (PSI) is used. The presentation will show multiple PSI results and assess their characteristics with respect to PS density and coverage. The PSI analysis is based on SAR data stacks from ERS-1/-2 C-band data (1996-2000), ERS-1/-2 & Envisat-ASAR C-band data (2002-2006) and ALOS-Palsar L-band data (2006-2011). For the assessment of the PSI results thematic data (geological, hydrogeological maps) as well as orthorectified optical images (IKONOS 2005) are used. All three PSI results show an overall pattern of increasing subsidence towards the coastline where the subsurface is built up by unconsolidated coastal sediments. However, the PSI results based on C-band SAR data show a lower PS density (< 100 PS/km2 versus > 500 PS/km2 in urban areas) and PS coverage (no PSs in areas with rural land cover in the PSI results based on C-band) compared to the PSI result based on L-band SAR data. The main reason for this differences is the longer wavelength of the L-band (λ = 23.6 cm) compared to the C-band (λ = 5.6 cm) resulting in less temporal phase decorrelation through an increased penetration depth and higher capability to detect fast displacements.

  13. Neuromimetic Circuits with Synaptic Devices Based on Strongly Correlated Electron Systems

    NASA Astrophysics Data System (ADS)

    Ha, Sieu D.; Shi, Jian; Meroz, Yasmine; Mahadevan, L.; Ramanathan, Shriram

    2014-12-01

    Strongly correlated electron systems such as the rare-earth nickelates (R NiO3 , R denotes a rare-earth element) can exhibit synapselike continuous long-term potentiation and depression when gated with ionic liquids; exploiting the extreme sensitivity of coupled charge, spin, orbital, and lattice degrees of freedom to stoichiometry. We present experimental real-time, device-level classical conditioning and unlearning using nickelate-based synaptic devices in an electronic circuit compatible with both excitatory and inhibitory neurons. We establish a physical model for the device behavior based on electric-field-driven coupled ionic-electronic diffusion that can be utilized for design of more complex systems. We use the model to simulate a variety of associate and nonassociative learning mechanisms, as well as a feedforward recurrent network for storing memory. Our circuit intuitively parallels biological neural architectures, and it can be readily generalized to other forms of cellular learning and extinction. The simulation of neural function with electronic device analogs may provide insight into biological processes such as decision making, learning, and adaptation, while facilitating advanced parallel information processing in hardware.

  14. On the acid-base properties of humic acid in soil.

    PubMed

    Cooke, James D; Hamilton-Taylor, John; Tipping, Edward

    2007-01-15

    Humic acid was isolated from three contrasting organic-rich soils and acid-base titrations performed over a range of ionic strengths. Results obtained were unlike most humic acid data sets; they showed a greater ionic strength dependency at low pH than at high pH. Forward- and back-titrations with the base and acid revealed hysteresis, particularly at low pH. Previous authors attributed this type of hysteresis to humic acid aggregates-created during the isolation procedure-being redissolved during titration as the pH increased and regarded the results as artificial. However, forward- and back-titrations with organic-rich soils also demonstrated a similar hysteretic behavior. These observations indicate (i) that titrations of humic acid in aggregated form (as opposed to the more usual dissolved form) are more representative of the acid-base properties of humic acid in soil and (ii) that the ionic strength dependency of proton binding in humic acid is related to its degree of aggregation. Thus, the current use of models based on data from dissolved humic substances to predictthe acid-base properties of humic acid in soil under environmental conditions may be flawed and could substantially overestimate their acid buffering capacity.

  15. Renal acid-base metabolism after ischemia.

    PubMed

    Holloway, J C; Phifer, T; Henderson, R; Welbourne, T C

    1986-05-01

    The response of the kidney to ischemia-induced cellular acidosis was followed over the immediate one hr post-ischemia reflow period. Clearance and extraction experiments as well as measurement of cortical intracellular pH (pHi) were performed on Inactin-anesthetized Sprague-Dawley rats. Arteriovenous concentration differences and para-aminohippurate extraction were obtained by cannulating the left renal vein. Base production was monitored as bicarbonate released into the renal vein and urine; net base production was related to the renal handling of glutamine and ammonia as well as to renal oxygen consumption and pHi. After a 15 min control period, the left renal artery was snared for one-half hr followed by release and four consecutive 15 min reflow periods. During the control period, cortical cell pHi measured by [14C]-5,5-Dimethyl-2,4-Oxazolidinedione distribution was 7.07 +/- 0.08, and Q-O2 was 14.1 +/- 2.2 micromoles/min; neither net glutamine utilization nor net bicarbonate generation occurred. After 30 min of ischemia, renal tissue pH fell to 6.6 +/- 0.15. However, within 45 min of reflow, cortical cell pH returned and exceeded the control value, 7.33 +/- 0.06 vs. 7.15 +/- 0.08. This increase in pHi was associated with a significant rise in cellular metabolic rate, Q-O2 increased to 20.3 +/- 6.4 micromoles/min. Corresponding with cellular alkalosis was a net production of bicarbonate and a net ammonia uptake and glutamine release; urinary acidification was abolished. These results are consistent with a nonexcretory renal metabolic base generating mechanism governing cellular acid base homeostasis following ischemia. PMID:3723929

  16. Quantitative determination of valproic acid in postmortem blood samples--evidence of strong matrix dependency and instability.

    PubMed

    Kiencke, Verena; Andresen-Streichert, Hilke; Müller, Alexander; Iwersen-Bergmann, Stefanie

    2013-11-01

    Most of the daily work of forensic toxicologists deals with fatal cases resulting from overdoses of licit and illicit drugs. However, another reason for fatalities in patients suffering from epilepsy can be undetectable or subtherapeutic levels of antiepileptic drugs. Some studies have shown a correlation between "sudden unexpected death in epilepsy" (SUDEP) and the ineffective treatment of epilepsy. Low levels of antiepileptic drugs may be a risk factor for SUDEP. The death of a psychiatric patient also suffering from epilepsy inspired the investigation. Subsequent to the death of the patient, the doctor was accused of providing inadequate therapy for epilepsy. The patient was to be treated with valproic acid. We developed and validated a simple method of determining valproic acid levels by gas chromatography-mass spectrometry for serum, but a transfer of the method from serum to postmortem whole blood failed. The method had to be modified and revalidated for postmortem whole blood specimens. A stability study of valproic acid in postmortem blood was conducted, showing a decline of valproic acid levels by 85 % after storage at room temperature for 28 days. During the storage time, the blood samples showed changes in consistency. Depending on the stage of decomposition, it is necessary to perform a determination by standard addition with an equilibration time of 4 h before extraction to achieve reliable results. For a proper interpretation of quantitative results, it is necessary to keep the postmortem decline of valproic acid concentrations in mind.

  17. A route for a strong increase of critical current in nanostrained iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Ozaki, Toshinori; Wu, Lijun; Zhang, Cheng; Jaroszynski, Jan; Si, Weidong; Zhou, Juan; Zhu, Yimei; Li, Qiang

    2016-10-01

    The critical temperature Tc and the critical current density Jc determine the limits to large-scale superconductor applications. Superconductivity emerges at Tc. The practical current-carrying capability, measured by Jc, is the ability of defects in superconductors to pin the magnetic vortices, and that may reduce Tc. Simultaneous increase of Tc and Jc in superconductors is desirable but very difficult to realize. Here we demonstrate a route to raise both Tc and Jc together in iron-based superconductors. By using low-energy proton irradiation, we create cascade defects in FeSe0.5Te0.5 films. Tc is enhanced due to the nanoscale compressive strain and proximity effect, whereas Jc is doubled under zero field at 4.2 K through strong vortex pinning by the cascade defects and surrounding nanoscale strain. At 12 K and above 15 T, one order of magnitude of Jc enhancement is achieved in both parallel and perpendicular magnetic fields to the film surface.

  18. Polymer/Pristine graphene based composites: from emulsions to strong, electrically conducting foams

    DOE PAGES

    Woltornist, Steven J.; Carrillo, Jan-Michael Y.; Xu, Thomas O.; Dobrynin, Andrey V.; Adamson, Douglas H.

    2015-01-21

    The unique electrical, thermal, and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water and common organic solvents have limited its practical utilization. In this paper, we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by overlapping pristine graphene sheets, enabling the synthesis of open cell foams containing a continuous graphitic network. Our approach utilizes the insolubility of graphene/graphite in both water and organic solvents and so does not require oxidation, reduction, surfactants, high boilingmore » solvents, chemical functionalization, or the input of large amounts of mechanical energy or heat. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. Finally, these emulsions are used as templates for the synthesis of open cell foams with densities below 0.35 g/cm3 that exhibit remarkable mechanical and electrical properties including compressive moduli up to ~100 MPa, compressive strengths of over 8.3 MPa (1200 psi), and bulk conductivities approaching 7 S/m.« less

  19. Polymer/Pristine graphene based composites: from emulsions to strong, electrically conducting foams

    SciTech Connect

    Woltornist, Steven J.; Carrillo, Jan-Michael Y.; Xu, Thomas O.; Dobrynin, Andrey V.; Adamson, Douglas H.

    2015-01-21

    The unique electrical, thermal, and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water and common organic solvents have limited its practical utilization. In this paper, we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by overlapping pristine graphene sheets, enabling the synthesis of open cell foams containing a continuous graphitic network. Our approach utilizes the insolubility of graphene/graphite in both water and organic solvents and so does not require oxidation, reduction, surfactants, high boiling solvents, chemical functionalization, or the input of large amounts of mechanical energy or heat. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. Finally, these emulsions are used as templates for the synthesis of open cell foams with densities below 0.35 g/cm3 that exhibit remarkable mechanical and electrical properties including compressive moduli up to ~100 MPa, compressive strengths of over 8.3 MPa (1200 psi), and bulk conductivities approaching 7 S/m.

  20. Quaternized dimethylaminoethyl methacrylate strong base anion exchange fibers for As(V) adsorption

    NASA Astrophysics Data System (ADS)

    Kavaklı, Cengiz; Akkaş Kavaklı, Pınar; Turan, Burcu Dila; Hamurcu, Aslı; Güven, Olgun

    2014-09-01

    N,N-Dimethylaminoethyl methacrylate (DMAEMA) grafted polyethylene/polypropylene (PE/PP) nonwoven fibers (DMAEMA-g-PE/PP) was prepared by radiation-induced graft polymerization. DMAEMA graft chains on nonwoven fibers were quaternized with dimethyl sulfate solution for the preparation of strong base anion exchange fibers (QDMAEMA-g-PE/PP). Fiber structures were characterized by FTIR, XPS and SEM techniques. The effect of solution pH, contact time, initial As(V) ion concentration and coexisting ions on the As(V) adsorption capacity of the QDMAEMA-g-PE/PP fibers were investigated by performing batch adsorption experiments. The adsorption of As(V) by QDMAEMA-g-PE/PP fibers was found to be independent on solution pH in the range 4.00-10.00. Kinetic experiments show that the As(V) adsorption rate was rapid and As(V) adsorption follows pseudo second-order kinetic model. As(V) adsorption equilibrium data were analyzed using Langmuir and Freundlich adsorption isotherm model equations. Langmuir and Freundlich adsorption isotherm models fitted the experimental data well. The maximum adsorption capacity (qmax) calculated from Langmuir isotherm was found to be 83.33 mg As(V)/g polymer at pH 7.00. The adsorbent was used for three cycles without significant loss of adsorption capacity. The adsorbed As(V) ions were desorbed effectively by a 0.1 M NaOH solution.

  1. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    PubMed Central

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis. PMID:27404510

  2. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting.

    PubMed

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis. PMID:27404510

  3. Active galaxies. A strong magnetic field in the jet base of a supermassive black hole.

    PubMed

    Martí-Vidal, Ivan; Muller, Sébastien; Vlemmings, Wouter; Horellou, Cathy; Aalto, Susanne

    2015-04-17

    Active galactic nuclei (AGN) host some of the most energetic phenomena in the universe. AGN are thought to be powered by accretion of matter onto a rotating disk that surrounds a supermassive black hole. Jet streams can be boosted in energy near the event horizon of the black hole and then flow outward along the rotation axis of the disk. The mechanism that forms such a jet and guides it over scales from a few light-days up to millions of light-years remains uncertain, but magnetic fields are thought to play a critical role. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have detected a polarization signal (Faraday rotation) related to the strong magnetic field at the jet base of a distant AGN, PKS 1830-211. The amount of Faraday rotation (rotation measure) is proportional to the integral of the magnetic field strength along the line of sight times the density of electrons. The high rotation measures derived suggest magnetic fields of at least tens of Gauss (and possibly considerably higher) on scales of the order of light-days (0.01 parsec) from the black hole. PMID:25883352

  4. Polymer/Pristine Graphene Based Composites: From Emulsions to Strong, Electrically Conducting Foams

    NASA Astrophysics Data System (ADS)

    Woltornist, Steven; Carrillo, Jan-Michael; Xu, Thomas; Dobrynin, Andrey; Adamson, Douglas

    2015-03-01

    The unique electrical, thermal and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water, common organic solvents, and polymer solutions and melts have limited its practical utilization. Here we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by a graphitic skin consisting of overlapping pristine graphene sheets that enables the synthesis of open cell foams containing a continuous graphitic skin network. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. These emulsions are used as templates for the synthesis of the open cell foams with densities below 0.35 g/cm3 and exhibiting remarkable mechanical and electrical properties including compressive moduli up to ~ 100 MPa, compressive strengths of over 8.3 MPa, and bulk conductivities approaching 7 S/m.

  5. A route for a strong increase of critical current in nanostrained iron-based superconductors

    PubMed Central

    Ozaki, Toshinori; Wu, Lijun; Zhang, Cheng; Jaroszynski, Jan; Si, Weidong; Zhou, Juan; Zhu, Yimei; Li, Qiang

    2016-01-01

    The critical temperature Tc and the critical current density Jc determine the limits to large-scale superconductor applications. Superconductivity emerges at Tc. The practical current-carrying capability, measured by Jc, is the ability of defects in superconductors to pin the magnetic vortices, and that may reduce Tc. Simultaneous increase of Tc and Jc in superconductors is desirable but very difficult to realize. Here we demonstrate a route to raise both Tc and Jc together in iron-based superconductors. By using low-energy proton irradiation, we create cascade defects in FeSe0.5Te0.5 films. Tc is enhanced due to the nanoscale compressive strain and proximity effect, whereas Jc is doubled under zero field at 4.2 K through strong vortex pinning by the cascade defects and surrounding nanoscale strain. At 12 K and above 15 T, one order of magnitude of Jc enhancement is achieved in both parallel and perpendicular magnetic fields to the film surface. PMID:27708268

  6. Active galaxies. A strong magnetic field in the jet base of a supermassive black hole.

    PubMed

    Martí-Vidal, Ivan; Muller, Sébastien; Vlemmings, Wouter; Horellou, Cathy; Aalto, Susanne

    2015-04-17

    Active galactic nuclei (AGN) host some of the most energetic phenomena in the universe. AGN are thought to be powered by accretion of matter onto a rotating disk that surrounds a supermassive black hole. Jet streams can be boosted in energy near the event horizon of the black hole and then flow outward along the rotation axis of the disk. The mechanism that forms such a jet and guides it over scales from a few light-days up to millions of light-years remains uncertain, but magnetic fields are thought to play a critical role. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have detected a polarization signal (Faraday rotation) related to the strong magnetic field at the jet base of a distant AGN, PKS 1830-211. The amount of Faraday rotation (rotation measure) is proportional to the integral of the magnetic field strength along the line of sight times the density of electrons. The high rotation measures derived suggest magnetic fields of at least tens of Gauss (and possibly considerably higher) on scales of the order of light-days (0.01 parsec) from the black hole.

  7. Water-Soluble Nonconjugated Polymer Nanoparticles with Strong Fluorescence Emission for Selective and Sensitive Detection of Nitro-Explosive Picric Acid in Aqueous Medium.

    PubMed

    Liu, Shi Gang; Luo, Dan; Li, Na; Zhang, Wei; Lei, Jing Lei; Li, Nian Bing; Luo, Hong Qun

    2016-08-24

    Water-soluble nonconjugated polymer nanoparticles (PNPs) with strong fluorescence emission were prepared from hyperbranched poly(ethylenimine) (PEI) and d-glucose via Schiff base reaction and self-assembly in aqueous phase. Preparation of the PEI-d-glucose (PEI-G) PNPs was facile (one-pot reaction) and environmentally friendly under mild conditions. Also, PEI-G PNPs showed a high fluorescence quantum yield in aqueous solution, and the fluorescence properties (such as concentration- and solvent-dependent fluorescence) and origin of intrinsic fluorescence were investigated and discussed. PEI-G PNPs were then used to develop a fluorescent probe for fast, selective, and sensitive detection of nitro-explosive picric acid (PA) in aqueous medium, because the fluorescence can be easily quenched by PA whereas other nitro-explosives and structurally similar compounds only caused negligible quenching. A wide linear range (0.05-70 μM) and a low detection limit (26 nM) were obtained. The fluorescence quenching mechanism was carefully explored, and it was due to a combined effect of electron transfer, resonance energy transfer, and inner filter effect between PA and PEI-G PNPs, which resulted in good selectivity and sensitivity for PA. Finally, the developed sensor was successfully applied to detection of PA in environmental water samples. PMID:27471907

  8. Conversion of corn stalk into furfural using a novel heterogeneous strong acid catalyst in γ-valerolactone.

    PubMed

    Xu, Zhiping; Li, Wenzhi; Du, Zhijie; Wu, Hao; Jameel, Hasan; Chang, Hou-Min; Ma, Longlong

    2015-12-01

    A novel solid acid catalyst was prepared by the copolymerization of p-toluenesulfonic acid and paraformaldehyde and then characterized by FT-IR, TG/DTG, HRTEM and N2-BET. Furfural was successfully produced by the dehydration of xylose and xylan using the novel catalyst in γ-valerolactone. This investigation focused on effects of various reaction conditions including solvent, acid catalyst, reaction temperature, residence time, water concentration, xylose loading and catalyst dosage on the dehydration of xylose to furfural. It was found that the solid catalyst displayed extremely high activity for furfural production. 80.4% furfural yield with 98.8% xylose conversion was achieved at 170°C for 10 min. The catalyst could be recycled at least five times without significant loss of activity. Furthermore, 83.5% furfural yield and 19.5% HMF yield were obtained from raw corn stalk under more severe conditions (190°C for 100 min).

  9. Base pairing and base mis-pairing in nucleic acids

    NASA Technical Reports Server (NTRS)

    Wang, A. H. J.; Rich, A.

    1986-01-01

    In recent years we have learned that DNA is conformationally active. It can exist in a number of different stable conformations including both right-handed and left-handed forms. Using single crystal X-ray diffraction analysis we are able to discover not only additional conformations of the nucleic acids but also different types of hydrogen bonded base-base interactions. Although Watson-Crick base pairings are the predominant type of interaction in double helical DNA, they are not the only types. Recently, we have been able to examine mismatching of guanine-thymine base pairs in left-handed Z-DNA at atomic resolution (1A). A minimum amount of distortion of the sugar phosphate backbone is found in the G x T pairing in which the bases are held together by two hydrogen bonds in the wobble pairing interaction. Because of the high resolution of the analysis we can visualize water molecules which fill in to accommodate the other hydrogen bonding positions in the bases which are not used in the base-base interactions. Studies on other DNA oligomers have revealed that other types of non-Watson-Crick hydrogen bonding interactions can occur. In the structure of a DNA octamer with the sequence d(GCGTACGC) complexed to an antibiotic triostin A, it was found that the two central AT base pairs are held together by Hoogsteen rather than Watson-Crick base pairs. Similarly, the G x C base pairs at the ends are also Hoogsteen rather than Watson-Crick pairing. Hoogsteen base pairs make a modified helix which is distinct from the Watson-Crick double helix.

  10. Dissociation of strong acid revisited: X-ray photoelectron spectroscopy and molecular dynamics simulations of HNO3 in water

    SciTech Connect

    Lewis, Tanza; Winter, Berndt; Stern, Abraham C.; Baer, Marcel D.; Mundy, Christopher J.; Tobias, Douglas J.; Hemminger, J. C.

    2011-08-04

    Molecular-level insight into the dissociation of nitric acid in water is obtained from photoelectron X-ray spectroscopy and first-principles molecular dynamics (MD) simulations. Our combined studies reveal surprisingly abrupt changes in solvation configurations of undissociated nitric acid at approximately 4 M concentration. Experimentally, this is inferred from N1s binding energy shifts of HNO3(aq) as a function of concentration, and is associated with variations in the local electronic structure of the nitrogen atom. It also shows up as a discontinuity in the degree of dissociation as a function of concentration, determined here from the N1s photoelectron signal intensity, which can be separately quantified for undissociated HNO3(aq) and dissociated NO3-(aq). Intermolecular interactions within the nitric acid solution are discussed on the basis of MD simulations, which reveal that molecular HNO3 interacts remarkably weakly with solvating water molecules at low concentration; around 4 M there is a turnover to a more structured solvation shell, accompanied by an increase in hydrogen bonding between HNO3 and water. We suggest that the driving force behind the more structured solvent configuration of HNO3 is the overlap of nitric acid solvent shells that sets in around 4 M concentration. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  11. Competition between Displacement and Dissociation of a Strong Acid Compared to a Weak Acid Adsorbed on Silica Particle Surfaces: The Role of Adsorbed Water.

    PubMed

    Fang, Yuan; Tang, Mingjin; Grassian, Vicki H

    2016-06-16

    The adsorption of nitric (HNO3) and formic (HCOOH) acids on silica particle surfaces and the effect of adsorbed water have been investigated at 296 K using transmission FTIR spectroscopy. Under dry conditions, both nitric and formic acids adsorb reversibly on silica. Additionally, the FTIR spectra show that both of these molecules remain in the protonated form. At elevated relative humidities (RH), adsorbed water competes both for surface adsorption sites with these acids as well as promotes their dissociation to hydronium ions and the corresponding anions. Compared to HNO3, the extent of dissociation is much smaller for HCOOH, very likely because it is a weaker acid. This study provides valuable insights into the interaction of HNO3 and HCOOH with silica surface on the molecular level and further reveals the complex roles of surface-adsorbed water in atmospheric heterogeneous chemistry of mineral dust particles-many of these containing silica.

  12. Competition between Displacement and Dissociation of a Strong Acid Compared to a Weak Acid Adsorbed on Silica Particle Surfaces: The Role of Adsorbed Water.

    PubMed

    Fang, Yuan; Tang, Mingjin; Grassian, Vicki H

    2016-06-16

    The adsorption of nitric (HNO3) and formic (HCOOH) acids on silica particle surfaces and the effect of adsorbed water have been investigated at 296 K using transmission FTIR spectroscopy. Under dry conditions, both nitric and formic acids adsorb reversibly on silica. Additionally, the FTIR spectra show that both of these molecules remain in the protonated form. At elevated relative humidities (RH), adsorbed water competes both for surface adsorption sites with these acids as well as promotes their dissociation to hydronium ions and the corresponding anions. Compared to HNO3, the extent of dissociation is much smaller for HCOOH, very likely because it is a weaker acid. This study provides valuable insights into the interaction of HNO3 and HCOOH with silica surface on the molecular level and further reveals the complex roles of surface-adsorbed water in atmospheric heterogeneous chemistry of mineral dust particles-many of these containing silica. PMID:27220375

  13. Designing CXCL8-based decoy proteins with strong anti-inflammatory activity in vivo

    PubMed Central

    Falsone, Angelika; Wabitsch, Veronica; Geretti, Elena; Potzinger, Heide; Gerlza, Tanja; Robinson, James; Adage, Tiziana; Teixeira, Mauro M.; Kungl, Andreas J.

    2013-01-01

    IL (interleukin)-8 [CXCL8 (CXC chemokine ligand 8)] exerts its role in inflammation by triggering neutrophils via its specific GPCRs (G-protein-coupled receptors), CXCR1 (CXC chemokine receptor 1) and CXCR2, for which additional binding to endothelial HS-GAGs (heparan sulphate-glycosaminoglycans) is required. We present here a novel approach for blocking the CXCL8-related inflammatory cascade by generating dominant-negative CXCL8 mutants with improved GAG-binding affinity and knocked-out CXCR1/CXCR2 activity. These non-signalling CXCL8 decoy proteins are able to displace WT (wild-type) CXCL8 and to prevent CXCR1/CXCR2 signalling thereby interfering with the inflammatory response. We have designed 14 CXCL8 mutants that we subdivided into three classes according to number and site of mutations. The decoys were characterized by IFTs (isothermal fluorescence titrations) and SPR (surface plasmon resonance) to determine GAG affinity. Protein stability and structural changes were evaluated by far-UV CD spectroscopy and knocked-out GPCR response was shown by Boyden chamber and Ca2+ release assays. From these experiments, CXCL8(Δ6F17KF21KE70KN71K) emerged with the most promising in vitro characteristics. This mutant was therefore further investigated in a murine model of mBSA (methylated BSA)-induced arthritis in mice where it showed strong anti-inflammatory activity. Based on these results, we propose that dominant-negative CXCL8 decoy proteins are a promising class of novel biopharmaceuticals with high therapeutic potential in inflammatory diseases. PMID:23919527

  14. History of medical understanding and misunderstanding of Acid base balance.

    PubMed

    Aiken, Christopher Geoffrey Alexander

    2013-09-01

    To establish how controversies in understanding acid base balance arose, the literature on acid base balance was reviewed from 1909, when Henderson described how the neutral reaction of blood is determined by carbonic and organic acids being in equilibrium with an excess of mineral bases over mineral acids. From 1914 to 1930, Van Slyke and others established our acid base principles. They recognised that carbonic acid converts into bicarbonate all non-volatile mineral bases not bound by mineral acids and determined therefore that bicarbonate represents the alkaline reserve of the body and should be a physiological constant. They showed that standard bicarbonate is a good measure of acidosis caused by increased production or decreased elimination of organic acids. However, they recognised that bicarbonate improved low plasma bicarbonate but not high urine acid excretion in diabetic ketoacidosis, and that increasing pCO2 caused chloride to shift into cells raising plasma titratable alkali. Both indicate that minerals influence pH. In 1945 Darrow showed that hyperchloraemic metabolic acidosis in preterm infants fed milk with 5.7 mmol of chloride and 2.0 mmol of sodium per 100 kcal was caused by retention of chloride in excess of sodium. Similar findings were made but not recognised in later studies of metabolic acidosis in preterm infants. Shohl in 1921 and Kildeberg in 1978 presented the theory that carbonic and organic acids are neutralised by mineral base, where mineral base is the excess of mineral cations over anions and organic acid is the difference between mineral base, bicarbonate and protein anion. The degree of metabolic acidosis measured as base excess is determined by deviation in both mineral base and organic acid from normal.

  15. Acid-Base Pairs in Lewis Acidic Zeolites Promote Direct Aldol Reactions by Soft Enolization.

    PubMed

    Lewis, Jennifer D; Van de Vyver, Stijn; Román-Leshkov, Yuriy

    2015-08-17

    Hf-, Sn-, and Zr-Beta zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions.

  16. Essentials in the diagnosis of acid-base disorders and their high altitude application.

    PubMed

    Paulev, P E; Zubieta-Calleja, G R

    2005-09-01

    This report describes the historical development in the clinical application of chemical variables for the interpretation of acid-base disturbances. The pH concept was already introduced in 1909. Following World War II, disagreements concerning the definition of acids and bases occurred, and since then two strategies have been competing. Danish scientists in 1923 defined an acid as a substance able to give off a proton at a given pH, and a base as a substance that could bind a proton, whereas the North American Singer-Hasting school in 1948 defined acids as strong non-buffer anions and bases as non-buffer cations. As a consequence of this last definition, electrolyte disturbances were mixed up with real acid-base disorders and the variable, strong ion difference (SID), was introduced as a measure of non-respiratory acid-base disturbances. However, the SID concept is only an empirical approximation. In contrast, the Astrup/Siggaard-Andersen school of scientists, using computer strategies and the Acid-base Chart, has made diagnosis of acid-base disorders possible at a glance on the Chart, when the data are considered in context with the clinical development. Siggaard-Andersen introduced Base Excess (BE) or Standard Base Excess (SBE) in the extracellular fluid volume (ECF), extended to include the red cell volume (eECF), as a measure of metabolic acid-base disturbances and recently replaced it by the term Concentration of Titratable Hydrogen Ion (ctH). These two concepts (SBE and ctH) represent the same concentration difference, but with opposite signs. Three charts modified from the Siggaard-Andersen Acid-Base Chart are presented for use at low, medium and high altitudes of 2500 m, 3500 m, and 4000 m, respectively. In this context, the authors suggest the use of Titratable Hydrogen Ion concentration Difference (THID) in the extended extracellular fluid volume, finding it efficient and better than any other determination of the metabolic component in acid-base

  17. Essentials in the diagnosis of acid-base disorders and their high altitude application.

    PubMed

    Paulev, P E; Zubieta-Calleja, G R

    2005-09-01

    This report describes the historical development in the clinical application of chemical variables for the interpretation of acid-base disturbances. The pH concept was already introduced in 1909. Following World War II, disagreements concerning the definition of acids and bases occurred, and since then two strategies have been competing. Danish scientists in 1923 defined an acid as a substance able to give off a proton at a given pH, and a base as a substance that could bind a proton, whereas the North American Singer-Hasting school in 1948 defined acids as strong non-buffer anions and bases as non-buffer cations. As a consequence of this last definition, electrolyte disturbances were mixed up with real acid-base disorders and the variable, strong ion difference (SID), was introduced as a measure of non-respiratory acid-base disturbances. However, the SID concept is only an empirical approximation. In contrast, the Astrup/Siggaard-Andersen school of scientists, using computer strategies and the Acid-base Chart, has made diagnosis of acid-base disorders possible at a glance on the Chart, when the data are considered in context with the clinical development. Siggaard-Andersen introduced Base Excess (BE) or Standard Base Excess (SBE) in the extracellular fluid volume (ECF), extended to include the red cell volume (eECF), as a measure of metabolic acid-base disturbances and recently replaced it by the term Concentration of Titratable Hydrogen Ion (ctH). These two concepts (SBE and ctH) represent the same concentration difference, but with opposite signs. Three charts modified from the Siggaard-Andersen Acid-Base Chart are presented for use at low, medium and high altitudes of 2500 m, 3500 m, and 4000 m, respectively. In this context, the authors suggest the use of Titratable Hydrogen Ion concentration Difference (THID) in the extended extracellular fluid volume, finding it efficient and better than any other determination of the metabolic component in acid-base

  18. Chip-based sequencing nucleic acids

    SciTech Connect

    Beer, Neil Reginald

    2014-08-26

    A system for fast DNA sequencing by amplification of genetic material within microreactors, denaturing, demulsifying, and then sequencing the material, while retaining it in a PCR/sequencing zone by a magnetic field. One embodiment includes sequencing nucleic acids on a microchip that includes a microchannel flow channel in the microchip. The nucleic acids are isolated and hybridized to magnetic nanoparticles or to magnetic polystyrene-coated beads. Microreactor droplets are formed in the microchannel flow channel. The microreactor droplets containing the nucleic acids and the magnetic nanoparticles are retained in a magnetic trap in the microchannel flow channel and sequenced.

  19. Assessment of acid-base balance. Stewart's approach.

    PubMed

    Fores-Novales, B; Diez-Fores, P; Aguilera-Celorrio, L J

    2016-04-01

    The study of acid-base equilibrium, its regulation and its interpretation have been a source of debate since the beginning of 20th century. Most accepted and commonly used analyses are based on pH, a notion first introduced by Sorensen in 1909, and on the Henderson-Hasselbalch equation (1916). Since then new concepts have been development in order to complete and make easier the understanding of acid-base disorders. In the early 1980's Peter Stewart brought the traditional interpretation of acid-base disturbances into question and proposed a new method. This innovative approach seems more suitable for studying acid-base abnormalities in critically ill patients. The aim of this paper is to update acid-base concepts, methods, limitations and applications.

  20. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1994-01-25

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 9 figures.

  1. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1996-07-23

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  2. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1994-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene disphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  3. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1996-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  4. Acid-base analysis: a critique of the Stewart and bicarbonate-centered approaches.

    PubMed

    Kurtz, Ira; Kraut, Jeffrey; Ornekian, Vahram; Nguyen, Minhtri K

    2008-05-01

    When approaching the analysis of disorders of acid-base balance, physical chemists, physiologists, and clinicians, tend to focus on different aspects of the relevant phenomenology. The physical chemist focuses on a quantitative understanding of proton hydration and aqueous proton transfer reactions that alter the acidity of a given solution. The physiologist focuses on molecular, cellular, and whole organ transport processes that modulate the acidity of a given body fluid compartment. The clinician emphasizes the diagnosis, clinical causes, and most appropriate treatment of acid-base disturbances. Historically, two different conceptual frameworks have evolved among clinicians and physiologists for interpreting acid-base phenomena. The traditional or bicarbonate-centered framework relies quantitatively on the Henderson-Hasselbalch equation, whereas the Stewart or strong ion approach utilizes either the original Stewart equation or its simplified version derived by Constable. In this review, the concepts underlying the bicarbonate-centered and Stewart formulations are analyzed in detail, emphasizing the differences in how each approach characterizes acid-base phenomenology at the molecular level, tissue level, and in the clinical realm. A quantitative comparison of the equations that are currently used in the literature to calculate H(+) concentration ([H(+)]) is included to clear up some of the misconceptions that currently exist in this area. Our analysis demonstrates that while the principle of electroneutrality plays a central role in the strong ion formulation, electroneutrality mechanistically does not dictate a specific [H(+)], and the strong ion and bicarbonate-centered approaches are quantitatively identical even in the presence of nonbicarbonate buffers. Finally, our analysis indicates that the bicarbonate-centered approach utilizing the Henderson-Hasselbalch equation is a mechanistic formulation that reflects the underlying acid-base phenomenology.

  5. Advances in nucleic acid-based detection methods.

    PubMed Central

    Wolcott, M J

    1992-01-01

    Laboratory techniques based on nucleic acid methods have increased in popularity over the last decade with clinical microbiologists and other laboratory scientists who are concerned with the diagnosis of infectious agents. This increase in popularity is a result primarily of advances made in nucleic acid amplification and detection techniques. Polymerase chain reaction, the original nucleic acid amplification technique, changed the way many people viewed and used nucleic acid techniques in clinical settings. After the potential of polymerase chain reaction became apparent, other methods of nucleic acid amplification and detection were developed. These alternative nucleic acid amplification methods may become serious contenders for application to routine laboratory analyses. This review presents some background information on nucleic acid analyses that might be used in clinical and anatomical laboratories and describes some recent advances in the amplification and detection of nucleic acids. PMID:1423216

  6. What is the Ultimate Goal in Acid-Base Regulation?

    ERIC Educational Resources Information Center

    Balakrishnan, Selvakumar; Gopalakrishnan, Maya; Alagesan, Murali; Prakash, E. Sankaranarayanan

    2007-01-01

    It is common to see chapters on acid-base physiology state that the goal of acid-base regulatory mechanisms is to maintain the pH of arterial plasma and not arterial PCO [subscript 2] (Pa[subscript CO[subscript 2

  7. A Closer Look at Acid-Base Olfactory Titrations

    ERIC Educational Resources Information Center

    Neppel, Kerry; Oliver-Hoyo, Maria T.; Queen, Connie; Reed, Nicole

    2005-01-01

    Olfactory titrations using raw onions and eugenol as acid-base indicators are reported. An in-depth investigation on olfactory titrations is presented to include requirements for potential olfactory indicators and protocols for using garlic, onions, and vanillin as acid-base olfactory indicators are tested.

  8. A Modern Approach to Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Drago, Russell S.

    1974-01-01

    Summarizes current status of our knowledge about acid-base interactions, including Lewis considerations, experimental design, data about donor-acceptor systems, common misconceptions, and hard-soft acid-base model. Indicates that there is the possibility of developing unifying concepts for chemical reactions of inorganic compounds. (CC)

  9. Connecting Acids and Bases with Encapsulation... and Chemistry with Nanotechnology

    ERIC Educational Resources Information Center

    Criswell, Brett

    2007-01-01

    The features and the development of various new acids and bases activity sets that combines chemistry with nanotechnology are being described. These sets lead to the generation of many nanotechnology-based pharmaceuticals for the treatment of various diseases.

  10. Trace analysis of acids and bases by conductometric titration with multiparametric non-linear regression.

    PubMed

    Coelho, Lúcia H G; Gutz, Ivano G R

    2006-03-15

    A chemometric method for analysis of conductometric titration data was introduced to extend its applicability to lower concentrations and more complex acid-base systems. Auxiliary pH measurements were made during the titration to assist the calculation of the distribution of protonable species on base of known or guessed equilibrium constants. Conductivity values of each ionized or ionizable species possibly present in the sample were introduced in a general equation where the only unknown parameters were the total concentrations of (conjugated) bases and of strong electrolytes not involved in acid-base equilibria. All these concentrations were adjusted by a multiparametric nonlinear regression (NLR) method, based on the Levenberg-Marquardt algorithm. This first conductometric titration method with NLR analysis (CT-NLR) was successfully applied to simulated conductometric titration data and to synthetic samples with multiple components at concentrations as low as those found in rainwater (approximately 10 micromol L(-1)). It was possible to resolve and quantify mixtures containing a strong acid, formic acid, acetic acid, ammonium ion, bicarbonate and inert electrolyte with accuracy of 5% or better.

  11. A Computer-Based Simulation of an Acid-Base Titration

    ERIC Educational Resources Information Center

    Boblick, John M.

    1971-01-01

    Reviews the advantages of computer simulated environments for experiments, referring in particular to acid-base titrations. Includes pre-lab instructions and a sample computer printout of a student's use of an acid-base simulation. Ten references. (PR)

  12. Folding study of Venus reveals a strong ion dependence of its yellow fluorescence under mildly acidic conditions.

    PubMed

    Hsu, Shang-Te Danny; Blaser, Georg; Behrens, Caroline; Cabrita, Lisa D; Dobson, Christopher M; Jackson, Sophie E

    2010-02-12

    Venus is a yellow fluorescent protein that has been developed for its fast chromophore maturation rate and bright yellow fluorescence that is relatively insensitive to changes in pH and ion concentrations. Here, we present a detailed study of the stability and folding of Venus in the pH range from 6.0 to 8.0 using chemical denaturants and a variety of spectroscopic probes. By following hydrogen-deuterium exchange of (15)N-labeled Venus using NMR spectroscopy over 13 months, residue-specific free energies of unfolding of some highly protected amide groups have been determined. Exchange rates of less than one per year are observed for some amide groups. A super-stable core is identified for Venus and compared with that previously reported for green fluorescent protein. These results are discussed in terms of the stability and folding of fluorescent proteins. Under mildly acidic conditions, we show that Venus undergoes a drastic decrease in yellow fluorescence at relatively low concentrations of guanidinium chloride. A detailed study of this effect establishes that it is due to pH-dependent, nonspecific interactions of ions with the protein. In contrast to previous studies on enhanced green fluorescence protein variant S65T/T203Y, which showed a specific halide ion-binding site, NMR chemical shift mapping shows no evidence for specific ion binding. Instead, chemical shift perturbations are observed for many residues primarily located in both lids of the beta-barrel structure, which suggests that small scale structural rearrangements occur on increasing ionic strength under mildly acidic conditions and that these are propagated to the chromophore resulting in fluorescence quenching.

  13. Nucleic acid duplexes incorporating a dissociable covalent base pair

    NASA Technical Reports Server (NTRS)

    Gao, K.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1999-01-01

    We have used molecular modeling techniques to design a dissociable covalently bonded base pair that can replace a Watson-Crick base pair in a nucleic acid with minimal distortion of the structure of the double helix. We introduced this base pair into a potential precursor of a nucleic acid double helix by chemical synthesis and have demonstrated efficient nonenzymatic template-directed ligation of the free hydroxyl groups of the base pair with appropriate short oligonucleotides. The nonenzymatic ligation reactions, which are characteristic of base paired nucleic acid structures, are abolished when the covalent base pair is reduced and becomes noncoplanar. This suggests that the covalent base pair linking the two strands in the duplex is compatible with a minimally distorted nucleic acid double-helical structure.

  14. Nucleic acid duplexes incorporating a dissociable covalent base pair.

    PubMed

    Gao, K; Orgel, L E

    1999-12-21

    We have used molecular modeling techniques to design a dissociable covalently bonded base pair that can replace a Watson-Crick base pair in a nucleic acid with minimal distortion of the structure of the double helix. We introduced this base pair into a potential precursor of a nucleic acid double helix by chemical synthesis and have demonstrated efficient nonenzymatic template-directed ligation of the free hydroxyl groups of the base pair with appropriate short oligonucleotides. The nonenzymatic ligation reactions, which are characteristic of base paired nucleic acid structures, are abolished when the covalent base pair is reduced and becomes noncoplanar. This suggests that the covalent base pair linking the two strands in the duplex is compatible with a minimally distorted nucleic acid double-helical structure. PMID:10611299

  15. Organic acids and bases: Review of toxicological studies

    SciTech Connect

    Leung, H.W.; Paustenbach, D.J. )

    1990-01-01

    Organic acids and bases are among the most frequently used chemicals in the manufacturing industries. However, the toxicology of only a number of them has been fully characterized, and for fewer still have occupational exposure limits been established. This paper reviews the acute and chronic toxicity data of the organic acids and bases, and considers the mechanism by which these chemicals produce their effects. A methodology for establishing preliminary occupational exposure limits based on the physicochemical properties of these chemicals is presented. Workplace exposure limits for 20 organic acids and bases which currently have no exposure guidelines are suggested. Advice regarding appropriate medical treatment of exposure to these materials is discussed. 98 references.

  16. General base-general acid catalysis by terpenoid cyclases.

    PubMed

    Pemberton, Travis A; Christianson, David W

    2016-07-01

    Terpenoid cyclases catalyze the most complex reactions in biology, in that more than half of the substrate carbon atoms often undergo changes in bonding during the course of a multistep cyclization cascade that proceeds through multiple carbocation intermediates. Many cyclization mechanisms require stereospecific deprotonation and reprotonation steps, and most cyclization cascades are terminated by deprotonation to yield an olefin product. The first bacterial terpenoid cyclase to yield a crystal structure was pentalenene synthase from Streptomyces exfoliatus UC5319. This cyclase generates the hydrocarbon precursor of the pentalenolactone family of antibiotics. The structures of pentalenene synthase and other terpenoid cyclases reveal predominantly nonpolar active sites typically lacking amino acid side chains capable of serving general base-general acid functions. What chemical species, then, enables the Brønsted acid-base chemistry required in the catalytic mechanisms of these enzymes? The most likely candidate for such general base-general acid chemistry is the co-product inorganic pyrophosphate. Here, we briefly review biological and nonbiological systems in which phosphate and its derivatives serve general base and general acid functions in catalysis. These examples highlight the fact that the Brønsted acid-base activities of phosphate derivatives are comparable to the Brønsted acid-base activities of amino acid side chains.

  17. Acid-base properties of 2-phenethyldithiocarbamoylacetic acid, an antitumor agent

    NASA Astrophysics Data System (ADS)

    Novozhilova, N. E.; Kutina, N. N.; Petukhova, O. A.; Kharitonov, Yu. Ya.

    2013-07-01

    The acid-base properties of the 2-phenethyldithiocarbamoylacetic acid (PET) substance belonging to the class of isothiocyanates and capable of inhibiting the development of tumors on many experimental models were studied. The acidity and hydrolysis constants of the PET substance in ethanol, acetone, aqueous ethanol, and aqueous acetone solutions were determined from the data of potentiometric (pH-metric) titration of ethanol and acetone solutions of PET with aqueous solidum hydroxide at room temperature.

  18. Hybrid magnetoresistance in Pt-based multilayers: Effect originated from strong interfacial spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Meng, Kangkang; Xiao, Jiaxing; Wu, Yong; Miao, Jun; Xu, Xiaoguang; Zhao, Jianhua; Jiang, Yong

    2016-02-01

    The hybrid magnetoresistance (MR) behaviors in Pt/Co90Fe10/Pt, Mn1.5Ga/Pt and Mn1.5Ga/Pt/Co90Fe10/Pt multilayers have been investigated. Both planer Hall effect (PHE) and angle-dependent MR in Pt/Co90Fe10/Pt revealed the combination of spin Hall MR (SMR) and normal anisotropic MR (AMR), indicating the large contribution of strong spin-orbit coupling (SOC) at the interfaces. When Pt contacted with perpendicular magnetic anisotropy (PMA) metal Mn1.5Ga, the strong interfacial SOC modified the effective anomalous Hall effect. The MR in Mn1.5Ga/Pt/Co90Fe10/Pt is not a simple combination of SMR and AMR, but ascribed to the complicated domain wall scattering and strong interfacial SOC when Pt is sandwiched by the in-plane magnetized Co90Fe10 and the PMA Mn1.5Ga.

  19. Hybrid magnetoresistance in Pt-based multilayers: Effect originated from strong interfacial spin-orbit coupling

    PubMed Central

    Meng, Kangkang; Xiao, Jiaxing; Wu, Yong; Miao, Jun; Xu, Xiaoguang; Zhao, Jianhua; Jiang, Yong

    2016-01-01

    The hybrid magnetoresistance (MR) behaviors in Pt/Co90Fe10/Pt, Mn1.5Ga/Pt and Mn1.5Ga/Pt/Co90Fe10/Pt multilayers have been investigated. Both planer Hall effect (PHE) and angle-dependent MR in Pt/Co90Fe10/Pt revealed the combination of spin Hall MR (SMR) and normal anisotropic MR (AMR), indicating the large contribution of strong spin-orbit coupling (SOC) at the interfaces. When Pt contacted with perpendicular magnetic anisotropy (PMA) metal Mn1.5Ga, the strong interfacial SOC modified the effective anomalous Hall effect. The MR in Mn1.5Ga/Pt/Co90Fe10/Pt is not a simple combination of SMR and AMR, but ascribed to the complicated domain wall scattering and strong interfacial SOC when Pt is sandwiched by the in-plane magnetized Co90Fe10 and the PMA Mn1.5Ga. PMID:26843035

  20. Alcohol Dimer is Requisite to Form an Alkyl Oxonium Ion in the Proton Transfer of a Strong (Photo)Acid to Alcohol.

    PubMed

    Park, Sun-Young; Lee, Young Min; Kwac, Kijeong; Jung, Yousung; Kwon, Oh-Hoon

    2016-03-18

    Alcohols, the simplest amphiprotic organic compounds, can exhibit either acidic or basic behavior by donating or accepting a proton. In this study, proton dissociation of a model photoacid in solution is explored by using time-resolved spectroscopy, revealing quantitatively for the first time that alcohol acts as a Brønsted base because of H-bonded cluster formation to enhance the reactivity. The protonated alcohol cluster, the alkyl oxonium ion, can be regarded as a key reaction intermediate in the well-established alcohol dehydration reaction. This finding signifies, as in water, the cooperativity of protic solvent molecules to facilitate nonaqueous acid-base reactions. PMID:26757097

  1. Succinic acid in levels produced by yeast (Saccharomyces cerevisiae) during fermentation strongly impacts wheat bread dough properties.

    PubMed

    Jayaram, Vinay B; Cuyvers, Sven; Verstrepen, Kevin J; Delcour, Jan A; Courtin, Christophe M

    2014-05-15

    Succinic acid (SA) was recently shown to be the major pH determining metabolite produced by yeast during straight-dough fermentation (Jayaram et al., 2013), reaching levels as high as 1.6 mmol/100 g of flour. Here, the impact of such levels of SA (0.8, 1.6 and 2.4 mmol/100 g flour) on yeastless dough properties was investigated. SA decreased the development time and stability of dough significantly. Uniaxial extension tests showed a consistent decrease in dough extensibility upon increasing SA addition. Upon biaxial extension in the presence of 2.4 mmol SA/100 g flour, a dough extensibility decrease of 47-65% and a dough strength increase of 25-40% were seen. While the SA solvent retention capacity of flour increased with increasing SA concentration in the solvent, gluten agglomeration decreased with gluten yield reductions of over 50%. The results suggest that SA leads to swelling and unfolding of gluten proteins, thereby increasing their interaction potential and dough strength, but simultaneously increasing intermolecular electrostatic repulsive forces. These phenomena lead to the reported changes in dough properties. Together, our results establish SA as an important yeast metabolite for dough rheology.

  2. Hybrid organic/inorganic copolymers with strongly hydrogen-bond acidic properties for acoustic wave and optical sensors

    SciTech Connect

    Grate, J.W.; Kaganove, S.N.; Patrash, S.J.

    1997-05-01

    Hybrid organic/inorganic polymers have been prepared incorporating fluoroalkyl-substituted bisphenol groups linked using oligosiloxane spacers. These hydrogen-bond acidic materials have glass-to-rubber transition temperatures below room temperature and are excellent sorbents for basic vapors. The physical properties such as viscosity and refractive index can be tuned by varying the length of the oligosiloxane spacers and the molecular weight. In addition, the materials are easily cross-linked to yield solid elastomers. The potential use of these materials for chemical sensing has been demonstrated by applying them to surface acoustic wave devices as thin films and detecting the hydrogen-bond basic vapor dimethyl methylphosphonate with high sensitivity. It has also been demonstrated that one of these materials with suitable viscosity and refractive index can be used to clad silica optical fibers; the cladding was applied to freshly drawn fiber using a fiber drawing tower. These fibers have potential as evanescent wave optical fiber sensors. 38 refs., 2 figs.

  3. Acid-base chemistry of white wine: analytical characterisation and chemical modelling.

    PubMed

    Prenesti, Enrico; Berto, Silvia; Toso, Simona; Daniele, Pier Giuseppe

    2012-01-01

    A chemical model of the acid-base properties is optimized for each white wine under study, together with the calculation of their ionic strength, taking into account the contributions of all significant ionic species (strong electrolytes and weak one sensitive to the chemical equilibria). Coupling the HPLC-IEC and HPLC-RP methods, we are able to quantify up to 12 carboxylic acids, the most relevant substances responsible of the acid-base equilibria of wine. The analytical concentration of carboxylic acids and of other acid-base active substances was used as input, with the total acidity, for the chemical modelling step of the study based on the contemporary treatment of overlapped protonation equilibria. New protonation constants were refined (L-lactic and succinic acids) with respect to our previous investigation on red wines. Attention was paid for mixed solvent (ethanol-water mixture), ionic strength, and temperature to ensure a thermodynamic level to the study. Validation of the chemical model optimized is achieved by way of conductometric measurements and using a synthetic "wine" especially adapted for testing.

  4. Acid-Base Chemistry of White Wine: Analytical Characterisation and Chemical Modelling

    PubMed Central

    Prenesti, Enrico; Berto, Silvia; Toso, Simona; Daniele, Pier Giuseppe

    2012-01-01

    A chemical model of the acid-base properties is optimized for each white wine under study, together with the calculation of their ionic strength, taking into account the contributions of all significant ionic species (strong electrolytes and weak one sensitive to the chemical equilibria). Coupling the HPLC-IEC and HPLC-RP methods, we are able to quantify up to 12 carboxylic acids, the most relevant substances responsible of the acid-base equilibria of wine. The analytical concentration of carboxylic acids and of other acid-base active substances was used as input, with the total acidity, for the chemical modelling step of the study based on the contemporary treatment of overlapped protonation equilibria. New protonation constants were refined (L-lactic and succinic acids) with respect to our previous investigation on red wines. Attention was paid for mixed solvent (ethanol-water mixture), ionic strength, and temperature to ensure a thermodynamic level to the study. Validation of the chemical model optimized is achieved by way of conductometric measurements and using a synthetic “wine” especially adapted for testing. PMID:22566762

  5. Reactive Distillation for Esterification of Bio-based Organic Acids

    SciTech Connect

    Fields, Nathan; Miller, Dennis J.; Asthana, Navinchandra S.; Kolah, Aspi K.; Vu, Dung; Lira, Carl T.

    2008-09-23

    The following is the final report of the three year research program to convert organic acids to their ethyl esters using reactive distillation. This report details the complete technical activities of research completed at Michigan State University for the period of October 1, 2003 to September 30, 2006, covering both reactive distillation research and development and the underlying thermodynamic and kinetic data required for successful and rigorous design of reactive distillation esterification processes. Specifically, this project has led to the development of economical, technically viable processes for ethyl lactate, triethyl citrate and diethyl succinate production, and on a larger scale has added to the overall body of knowledge on applying fermentation based organic acids as platform chemicals in the emerging biorefinery. Organic acid esters constitute an attractive class of biorenewable chemicals that are made from corn or other renewable biomass carbohydrate feedstocks and replace analogous petroleum-based compounds, thus lessening U.S. dependence on foreign petroleum and enhancing overall biorefinery viability through production of value-added chemicals in parallel with biofuels production. Further, many of these ester products are candidates for fuel (particularly biodiesel) components, and thus will serve dual roles as both industrial chemicals and fuel enhancers in the emerging bioeconomy. The technical report from MSU is organized around the ethyl esters of four important biorenewables-based acids: lactic acid, citric acid, succinic acid, and propionic acid. Literature background on esterification and reactive distillation has been provided in Section One. Work on lactic acid is covered in Sections Two through Five, citric acid esterification in Sections Six and Seven, succinic acid in Section Eight, and propionic acid in Section Nine. Section Ten covers modeling of ester and organic acid vapor pressure properties using the SPEAD (Step Potential

  6. On the formation of proton-shared and contact ion pair forms during the dissociation of moderately strong acids: an Ab initio molecular dynamics investigation.

    PubMed

    Thomas, Vibin; Maurer, Patrick; Iftimie, Radu

    2010-06-24

    Acid ionization and dissociation are phenomena that play a fundamental role in chemistry and biology, but their microscopic details are largely unknown. We use ab initio molecular dynamics to identify and characterize various structures that are formed along the pathway of dissociation of trifluoroacetic acid (pK(a) = 0.5). The present results demonstrate that solutions of moderately strong (-1 acids contain significant quantities of at least two forms whose bonding patterns are intermediate between those of covalent and dissociated structures, R-COOH...OH(2) and R-COO(-)(aq) + H(3)O(+)(aq), respectively. The first is a proton-shared structure of the form R-COO(delta-).H.(delta+)OH(2) which can be distinguished from the covalent form by its characteristic "continuous" absorption below 1700 cm(-1). The second is a contact ion pair whose average structure can be written as R-COO(-).H(3)O(+). We demonstrate that the transformation of proton-shared into contact ion pair forms coincides with the disappearance of the carbonyl vibration mode centered around 1720 cm(-1) and the appearance of the asymmetric and symmetric carboxylate [Formula: see text] vibration modes at 1620 and 1380 cm(-1), respectively. The aforementioned transformation is accompanied by significant changes in the first solvation shell of the acid molecule which we discuss.

  7. Feed frequency in a sequencing batch reactor strongly affects the production of polyhydroxyalkanoates (PHAs) from volatile fatty acids.

    PubMed

    Valentino, Francesco; Beccari, Mario; Fraraccio, Serena; Zanaroli, Giulio; Majone, Mauro

    2014-06-25

    The production of polyhydroxyalkanoates (PHAs) by activated sludge selected in a sequencing batch reactor (SBR) has been investigated. Several SBR runs were performed at the same applied organic load rate (OLR), hydraulic retention time (HRT) and feed concentration (8.5 g COD L(-1) of volatile fatty acids, VFAs) under aerobic conditions. The effect of the feeding time was only evaluated with a cycle length of 8h; for this particular cycle length, an increase in the storage response was observed by increasing the rate at which the substrate was fed into the reactor (at a fixed feeding frequency). Furthermore, a significantly stronger effect was observed by decreasing the cycle length from 8h to 6h and then to 2h, changing the feed frequency or changing the organic load given per cycle (all of the other conditions remained the same): the length of the feast phase decreased from 26 to 20.0 and then to 19.7% of the overall cycle length, respectively, due to an increase in the substrate removal rate. This removal rate was high and similar for the runs with cycle lengths of 2h and 6h in the SBR. This result was due to an increase in the selective pressure and the specific storage properties of the selected biomass. The highest polymer productivity after long-term accumulation batch tests was 1.7 g PHA L(-1)d(-1), with PHA content in the biomass of approximately 50% on a COD basis under nitrogen limitation. The DGGE profiles showed that the good storage performance correlated to the development of Lampropedia hyalina, which was only observed in the SBR runs characterized by a shorter cycle length.

  8. Cross-linked, biodegradable, cytocompatible salicylic acid based polyesters for localized, sustained delivery of salicylic acid: an in vitro study.

    PubMed

    Chandorkar, Yashoda; Bhagat, Rajesh K; Madras, Giridhar; Basu, Bikramjit

    2014-03-10

    In order to suppress chronic inflammation while supporting cell proliferation, there has been a continuous surge toward development of polymers with the intention of delivering anti-inflammatory molecules in a sustained manner. In the above backdrop, we report the synthesis of a novel, stable, cross-linked polyester with salicylic acid (SA) incorporated in the polymeric backbone and propose a simple synthesis route by melt condensation. The as-synthesized polymer was hydrophobic with a glass transition temperature of 1 °C, which increases to 17 °C upon curing. The combination of NMR and FT-IR spectral techniques established the ester linkages in the as-synthesized SA-based polyester. The pH-dependent degradation rate and the rate of release of salicylic acid from the as-synthesized SA-based polymer were studied at physiological conditions in vitro. The polyester underwent surface erosion and exhibited linear degradation kinetics in which a change in degradation rate is observed after 4-10 days and 24% mass loss was recorded after 4 months at 37 °C and pH 7.4. The delivery of salicylic acid also showed a similar change in slopes, with a sustained release rate of 3.5% in 4 months. The cytocompatibility studies of these polyesters were carried out with C2C12 murine myoblast cells using techniques like MTT assay and flow cytometry. Our results strongly suggest that SA-based polyester supports cell proliferation for 3 days in culture and do not cause cell death (<7%), as quantified by propidium iodide (PI) stained cells. Hence, these polyesters can be used as implant materials for localized, sustained delivery of salicylic acid and have applications in adjuvant cancer therapy, chronic wound healing, and as an alternative to commercially available polymers like poly(lactic acid) and poly(glycolic acid) or their copolymers.

  9. TREATMENT FOR IMPROVING THE OPERATION OF STRONG BASE ANION EXCHANGE RESINS

    DOEpatents

    Stevenson, P.C.

    1960-11-29

    A process is offered for improving quaternary ammonium type strongly basic anion exchange resins so that centain zinc and cadmium residues, which normally stick to and "poison" this type of resin, can be removed by elution. Specifically, the resin as obtained commercially is treated with an aqueous solution of sodium hydroxide of about 1 to 4 M concentration by heating therein and periodically adding small amounts of oxidizing agent selected from hydrogen peroxide, sodium peroxide and hypochlorite. Zinc and cadmium values may then be adsorbed onto the resin from a 0.1 to 3 M HCl and thereafter eluted therefrom with very dilute HCl solutions.

  10. Polymerization of amino acids containing nucleotide bases

    NASA Technical Reports Server (NTRS)

    Ben Cheikh, Azzouz; Orgel, Leslie E.

    1990-01-01

    The nucleoamino acids 1-(3'-amino,3'-carboxypropyl)uracil (3) and 9-(3'-amino,3'-carboxypropyl)adenine (4) have been prepared as (L)-en-antiomers and as racemic mixtures. When 3 or 4 is suspended in water and treated with N,N'-carbon-yldiimidazole, peptides are formed in good yield. The products formed from the (L)-enantiomers are hydrolyzed to the monomeric amino acids by pronase. Attempts to improve the efficiency of these oligomerizations by including a polyuridylate template in the reaction mixture were not successful. Similarly, oligomers derived from the (L)-enantiomer of 3 did not act as templates to facilitate the oligomerization of 4.

  11. Fabrication and photoluminescence of strong phase-separated InGaN based nanopillar LEDs

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Zhu, Chuanrui; Zhou, Yufan; Wang, Xuesong; Liu, Baoli; Wang, Xuelin; Lv, Yuanjie; Feng, Zhihong; Xu, Xiangang; Ji, Ziwu

    2015-12-01

    A strong phase-separated InGaN/GaN multiple quantum well (MQW) light-emitting diode (LED) producing a blue-green dual-wavelength spectrum has been grown, and fabricated into two nanopillar array structures with different etching depths: one fabricated only on the p-GaN layer and the other penetrating through the active layers. Micro-photoluminescence (μ-PL) spectra have shown that compared with the as-grown (planar) LED, light extraction efficiency (LEE) is improved for both the shorter and the longer nanopillar array structures due to the increased light-extracting surface area and light-guiding effect, in contrast, internal quantum efficiency (IQE) is improved for only the longer one due to the relaxation of strain in the MQWs embedded in the nanopillars. Furthermore, the strain relaxation-induced peak blue-shift value is smaller for the green emission from In-rich quantum dots (QDs) than the blue emission from the InGaN matrix, and decreases for both the emissions with increasing temperature. The former is attributed to the quantum-confined Stark effect (QCSE) in the strong localized QDs of small size being smaller than in the InGaN matrix, the latter is due to the decrease of the thermal-mismatch strain in the MQWs with increasing temperature.

  12. Bioinspired Surface for Surgical Graspers Based on the Strong Wet Friction of Tree Frog Toe Pads.

    PubMed

    Chen, Huawei; Zhang, Liwen; Zhang, Deyuan; Zhang, Pengfei; Han, Zhiwu

    2015-07-01

    Soft tissue damage is often at risk during the use of a surgical grasper, because of the strong holding force required to prevent slipping of the soft tissue in wet surgical environments. Improvement of wet friction properties at the interface between the surgical grasper and soft tissue can greatly reduce the holding force required and, thus, the soft tissue damage. To design and fabricate a biomimetic microscale surface with strong wet friction, the wet attachment mechanism of tree frog toe pads was investigated by observing their epithelial cell structure and the directionally dependent friction on their toe pads. Using these observations as inspiration, novel surface micropatterns were proposed for the surface of surgical graspers. The wet friction of biomimetic surfaces with various types of polygon pillar patterns involving quadrangular pillars, triangular pillars, rhomboid pillars, and varied hexagonal pillars were tested. The hexagonal pillar pattern exhibited improved wet frictional performance over the modern surgical grasper jaw pattern, which has conventional macroscale teeth. Moreover, the deformation of soft tissue in the bioinspired surgical grasper with a hexagonal pillar pattern is decreased, compared with the conventional surgical grasper.

  13. Importance of acid-base equilibrium in electrocatalytic oxidation of formic acid on platinum.

    PubMed

    Joo, Jiyong; Uchida, Taro; Cuesta, Angel; Koper, Marc T M; Osawa, Masatoshi

    2013-07-10

    Electro-oxidation of formic acid on Pt in acid is one of the most fundamental model reactions in electrocatalysis. However, its reaction mechanism is still a matter of strong debate. Two different mechanisms, bridge-bonded adsorbed formate mechanism and direct HCOOH oxidation mechanism, have been proposed by assuming a priori that formic acid is the major reactant. Through systematic examination of the reaction over a wide pH range (0-12) by cyclic voltammetry and surface-enhanced infrared spectroscopy, we show that the formate ion is the major reactant over the whole pH range examined, even in strong acid. The performance of the reaction is maximal at a pH close to the pKa of formic acid. The experimental results are reasonably explained by a new mechanism in which formate ion is directly oxidized via a weakly adsorbed formate precursor. The reaction serves as a generic example illustrating the importance of pH variation in catalytic proton-coupled electron-transfer reactions.

  14. The acid-base titration of montmorillonite

    NASA Astrophysics Data System (ADS)

    Bourg, I. C.; Sposito, G.; Bourg, A. C.

    2003-12-01

    Proton binding to clay minerals plays an important role in the chemical reactivity of soils (e.g., acidification, retention of nutrients or pollutants). If should also affect the performance of clay barriers for waste disposal. The surface acidity of clay minerals is commonly modelled empirically by assuming generic amphoteric surface sites (>SOH) on a flat surface, with fitted site densities and acidity constant. Current advances in experimental methods (notably spectroscopy) are rapidly improving our understanding of the structure and reactivity of the surface of clay minerals (arrangement of the particles, nature of the reactive surface sites, adsorption mechanisms). These developments are motivated by the difficulty of modelling the surface chemistry of mineral surfaces at the macro-scale (e.g., adsorption or titration) without a detailed (molecular-scale) picture of the mechanisms, and should be progressively incorporated into surface complexation models. In this view, we have combined recent estimates of montmorillonite surface properties (surface site density and structure, edge surface area, surface electrostatic potential) with surface site acidities obtained from the titration of alpha-Al2O3 and SiO2, and a novel method of accounting for the unknown initial net proton surface charge of the solid. The model predictions were compared to experimental titrations of SWy-1 montmorillonite and purified MX-80 bentonite in 0.1-0.5 mol/L NaClO4 and 0.005-0.5 mol/L NaNO3 background electrolytes, respectively. Most of the experimental data were appropriately described by the model after we adjusted a single parameter (silanol sites on the surface of montmorillonite were made to be slightly more acidic than those of silica). At low ionic strength and acidic pH the model underestimated the buffering capacity of the montmorillonite, perhaps due to clay swelling or to the interlayer adsorption of dissolved aluminum. The agreement between our model and the experimental

  15. Differential titration of bases in glacial acetic acid.

    PubMed

    Castellano, T; Medwick, T; Shinkai, J H; Bailey, L

    1981-01-01

    A study of bases in acetic acid and their differential titration was carried out. The overall basicity constants for 20 bases were measured in acetic acid, and the differential titration of five binary mixtures of variable delta pKb values in acetic acid was followed using a glass electrode-modified calomel electrode system. Agreement with literature values was good. A leveling diagram was constructed that indicated that bases stronger than aqueous pKb 10 are leveled to an acetous pKb 5.69, whereas weaker bases are not leveled but instead exhibit their own intrinsic basicity, with the acetous pKb to aqueous pKb values being linearly related (slope 1.18, correlation coefficient 0.962). A minimum acetous delta pKb of four units is required for the satisfactory differential titration of two bases in acetic acid.

  16. Acid-base status in dietary treatment of phenylketonuria.

    PubMed

    Manz, F; Schmidt, H; Schärer, K; Bickel, H

    1977-10-01

    Blood acid-base status, serum electrolytes, and urine pH were examined in 64 infants and children with phenylketonuria (PKU) treated with three different low phenylalanine protein hydrolyzates (Aponti, Cymogran, AlbumaidXP) and two synthetic amino acid mixtures (Aminogran, PAM). The formulas caused significant differences in acid-base status, serum potassium, and chloride, and in urine pH. In acid-base balance studies in two patients with PKU, Aponti, PAM, and two modifications of PAM (P2 + P3) were given. We observed a change from mild alkalosis to increasing metabolic acidosis from Aponti (serum bicarbonate 25,8 mval/liter) to P3 (24,0Y, P2 (19, 3) and PAM (17,0). Urine pH decreased and renal net acid excretion increased. In the formulas PAM, P2 and P3 differences in renal net acid excretion correlated with differences in chloride and sulfur contents of the diets and of the urines. New modifications of AlbumaidXP and of PAM, prepared according to our recommendations, showed normal renal net acid excretion (1 mEq/kg/24 hr) in a balance study performed in one patient with PKU and normal acid base status in 20 further patients.

  17. Nucleic acid based fluorescent sensor for mercury detection

    DOEpatents

    Lu, Yi; Liu, Juewen

    2013-02-05

    A nucleic acid enzyme comprises an oligonucleotide containing thymine bases. The nucleic acid enzyme is dependent on both Hg.sup.2+and a second ion as cofactors, to produce a product from a substrate. The substrate comprises a ribonucleotide, a deoxyribonucleotide, or both.

  18. Hyaluronic Acid Based Hydrogels for Regenerative Medicine Applications.

    PubMed

    Borzacchiello, Assunta; Russo, Luisa; Malle, Birgitte M; Schwach-Abdellaoui, Khadija; Ambrosio, Luigi

    2015-01-01

    Hyaluronic acid (HA) hydrogels, obtained by cross-linking HA molecules with divinyl sulfone (DVS) based on a simple, reproducible, and safe process that does not employ any organic solvents, were developed. Owing to an innovative preparation method the resulting homogeneous hydrogels do not contain any detectable residual cross-linking agent and are easier to inject through a fine needle. HA hydrogels were characterized in terms of degradation and biological properties, viscoelasticity, injectability, and network structural parameters. They exhibit a rheological behaviour typical of strong gels and show improved viscoelastic properties by increasing HA concentration and decreasing HA/DVS weight ratio. Furthermore, it was demonstrated that processes such as sterilization and extrusion through clinical needles do not imply significant alteration of viscoelastic properties. Both SANS and rheological tests indicated that the cross-links appear to compact the network, resulting in a reduction of the mesh size by increasing the cross-linker amount. In vitro degradation tests of the HA hydrogels demonstrated that these new hydrogels show a good stability against enzymatic degradation, which increases by increasing HA concentration and decreasing HA/DVS weight ratio. Finally, the hydrogels show a good biocompatibility confirmed by in vitro tests. PMID:26090451

  19. Hyaluronic Acid Based Hydrogels for Regenerative Medicine Applications

    PubMed Central

    Borzacchiello, Assunta; Russo, Luisa; Malle, Birgitte M.; Schwach-Abdellaoui, Khadija; Ambrosio, Luigi

    2015-01-01

    Hyaluronic acid (HA) hydrogels, obtained by cross-linking HA molecules with divinyl sulfone (DVS) based on a simple, reproducible, and safe process that does not employ any organic solvents, were developed. Owing to an innovative preparation method the resulting homogeneous hydrogels do not contain any detectable residual cross-linking agent and are easier to inject through a fine needle. HA hydrogels were characterized in terms of degradation and biological properties, viscoelasticity, injectability, and network structural parameters. They exhibit a rheological behaviour typical of strong gels and show improved viscoelastic properties by increasing HA concentration and decreasing HA/DVS weight ratio. Furthermore, it was demonstrated that processes such as sterilization and extrusion through clinical needles do not imply significant alteration of viscoelastic properties. Both SANS and rheological tests indicated that the cross-links appear to compact the network, resulting in a reduction of the mesh size by increasing the cross-linker amount. In vitro degradation tests of the HA hydrogels demonstrated that these new hydrogels show a good stability against enzymatic degradation, which increases by increasing HA concentration and decreasing HA/DVS weight ratio. Finally, the hydrogels show a good biocompatibility confirmed by in vitro tests. PMID:26090451

  20. Potentiometric Measurement of Transition Ranges and Titration Errors for Acid/Base Indicators

    NASA Astrophysics Data System (ADS)

    Flowers, Paul A.

    1997-07-01

    Sophomore analytical chemistry courses typically devote a substantial amount of lecture time to acid/base equilibrium theory, and usually include at least one laboratory project employing potentiometric titrations. In an effort to provide students a laboratory experience that more directly supports their classroom discussions on this important topic, an experiment involving potentiometric measurement of transition ranges and titration errors for common acid/base indicators has been developed. The pH and visually-assessed color of a millimolar strong acid/base system are monitored as a function of added titrant volume, and the resultant data plotted to permit determination of the indicator's transition range and associated titration error. Student response is typically quite positive, and the measured quantities correlate reasonably well to literature values.

  1. Acid-base titration curves for acids with very small ratios of successive dissociation constants.

    PubMed

    Campbell, B H; Meites, L

    1974-02-01

    The shapes of the potentiometric acid-base titration curves obtained in the neutralizations of polyfunctional acids or bases for which each successive dissociation constant is smaller than the following one are examined. In the region 0 < < 1 (where is the fraction of the equivalent volume of reagent that has been added) the slope of the titration curve decreases as the number j of acidic or basic sites increases. The difference between the pH-values at = 0.75 and = 0.25 has (1 j)log 9 as the lower limit of its maximum value.

  2. Renal acidification responses to respiratory acid-base disorders.

    PubMed

    Madias, Nicolaos E

    2010-01-01

    Respiratory acid-base disorders are those abnormalities in acid-base equilibrium that are expressed as primary changes in the arterial carbon dioxide tension (PaCO2). An increase in PaCO2 (hypercapnia) acidifies body fluids and initiates the acid-base disturbance known as respiratory acidosis. By contrast, a decrease in PaCO2 (hypocapnia) alkalinizes body fluids and initiates the acid-base disturbance known as respiratory alkalosis. The impact on systemic acidity of these primary changes in PaCO2 is ameliorated by secondary, directional changes in plasma [HCO3¯] that occur in 2 stages. Acutely, hypercapnia or hypocapnia yields relatively small changes in plasma [HCO3¯] that originate virtually exclusively from titration of the body's nonbicarbonate buffers. During sustained hypercapnia or hypocapnia, much larger changes in plasma [HCO3¯] occur that reflect adjustments in renal acidification mechanisms. Consequently, the deviation of systemic acidity from normal is smaller in the chronic forms of these disorders. Here we provide an overview of the renal acidification responses to respiratory acid-base disorders. We also identify gaps in knowledge that require further research.

  3. An Olfactory Indicator for Acid-Base Titrations.

    ERIC Educational Resources Information Center

    Flair, Mark N.; Setzer, William N.

    1990-01-01

    The use of an olfactory acid-base indicator in titrations for visually impaired students is discussed. Potential olfactory indicators include eugenol, thymol, vanillin, and thiophenol. Titrations performed with each indicator with eugenol proved to be successful. (KR)

  4. Biologist's Toolbox. Acid-base Balance: An Educational Computer Game.

    ERIC Educational Resources Information Center

    Boyle, Joseph, III; Robinson, Gloria

    1987-01-01

    Describes a microcomputer program that can be used in teaching the basic physiological aspects of acid-base (AB) balance. Explains how its game format and graphic approach can be applied in diagnostic and therapeutic exercises. (ML)

  5. Towards lactic acid bacteria-based biorefineries.

    PubMed

    Mazzoli, Roberto; Bosco, Francesca; Mizrahi, Itzhak; Bayer, Edward A; Pessione, Enrica

    2014-11-15

    Lactic acid bacteria (LAB) have long been used in industrial applications mainly as starters for food fermentation or as biocontrol agents or as probiotics. However, LAB possess several characteristics that render them among the most promising candidates for use in future biorefineries in converting plant-derived biomass-either from dedicated crops or from municipal/industrial solid wastes-into biofuels and high value-added products. Lactic acid, their main fermentation product, is an attractive building block extensively used by the chemical industry, owing to the potential for production of polylactides as biodegradable and biocompatible plastic alternative to polymers derived from petrochemicals. LA is but one of many high-value compounds which can be produced by LAB fermentation, which also include biofuels such as ethanol and butanol, biodegradable plastic polymers, exopolysaccharides, antimicrobial agents, health-promoting substances and nutraceuticals. Furthermore, several LAB strains have ascertained probiotic properties, and their biomass can be considered a high-value product. The present contribution aims to provide an extensive overview of the main industrial applications of LAB and future perspectives concerning their utilization in biorefineries. Strategies will be described in detail for developing LAB strains with broader substrate metabolic capacity for fermentation of cheaper biomass.

  6. Towards lactic acid bacteria-based biorefineries.

    PubMed

    Mazzoli, Roberto; Bosco, Francesca; Mizrahi, Itzhak; Bayer, Edward A; Pessione, Enrica

    2014-11-15

    Lactic acid bacteria (LAB) have long been used in industrial applications mainly as starters for food fermentation or as biocontrol agents or as probiotics. However, LAB possess several characteristics that render them among the most promising candidates for use in future biorefineries in converting plant-derived biomass-either from dedicated crops or from municipal/industrial solid wastes-into biofuels and high value-added products. Lactic acid, their main fermentation product, is an attractive building block extensively used by the chemical industry, owing to the potential for production of polylactides as biodegradable and biocompatible plastic alternative to polymers derived from petrochemicals. LA is but one of many high-value compounds which can be produced by LAB fermentation, which also include biofuels such as ethanol and butanol, biodegradable plastic polymers, exopolysaccharides, antimicrobial agents, health-promoting substances and nutraceuticals. Furthermore, several LAB strains have ascertained probiotic properties, and their biomass can be considered a high-value product. The present contribution aims to provide an extensive overview of the main industrial applications of LAB and future perspectives concerning their utilization in biorefineries. Strategies will be described in detail for developing LAB strains with broader substrate metabolic capacity for fermentation of cheaper biomass. PMID:25087936

  7. Characteristics of weak base-induced vacuoles formed around individual acidic organelles.

    PubMed

    Hiruma, Hiromi; Kawakami, Tadashi

    2011-01-01

    We have previously found that the weak base 4-aminopyridine induces Brownian motion of acidic organelles around which vacuoles are formed, causing organelle traffic disorder in neurons. Our present study investigated the characteristics of vacuoles induced by weak bases (NH(4)Cl, aminopyridines, and chloroquine) using mouse cells. Individual vacuoles included acidic organelles identified by fluorescent protein expression. Mitochondria and actin filaments were extruded outside the vacuoles, composing the vacuole rim. Staining with amine-reactive fluorescence showed no protein/amino acid content in vacuoles. Thus, serous vacuolar contents are probably partitioned by viscous cytosol, other organelles, and cytoskeletons, but not membrane. The weak base (chloroquine) was immunochemically detected in intravacuolar organelles, but not in vacuoles. Early vacuolization was reversible, but long-term vacuolization caused cell death. The vacuolization and cell death were blocked by the vacuolar H(+)-ATPase inhibitor and Cl--free medium. Staining with LysoTracker or LysoSensor indicated that intravacuolar organelles were strongly acidic and vacuoles were slightly acidic. This suggests that vacuolization is caused by accumulation of weak base and H(+) in acidic organelles, driven by vacuolar H(+)-ATPase associated with Cl(-) entering, and probably by subsequent extrusion of H(+) and water from organelles to the surrounding cytoplasm. PMID:21744328

  8. Characteristics of weak base-induced vacuoles formed around individual acidic organelles.

    PubMed

    Hiruma, Hiromi; Kawakami, Tadashi

    2011-01-01

    We have previously found that the weak base 4-aminopyridine induces Brownian motion of acidic organelles around which vacuoles are formed, causing organelle traffic disorder in neurons. Our present study investigated the characteristics of vacuoles induced by weak bases (NH(4)Cl, aminopyridines, and chloroquine) using mouse cells. Individual vacuoles included acidic organelles identified by fluorescent protein expression. Mitochondria and actin filaments were extruded outside the vacuoles, composing the vacuole rim. Staining with amine-reactive fluorescence showed no protein/amino acid content in vacuoles. Thus, serous vacuolar contents are probably partitioned by viscous cytosol, other organelles, and cytoskeletons, but not membrane. The weak base (chloroquine) was immunochemically detected in intravacuolar organelles, but not in vacuoles. Early vacuolization was reversible, but long-term vacuolization caused cell death. The vacuolization and cell death were blocked by the vacuolar H(+)-ATPase inhibitor and Cl--free medium. Staining with LysoTracker or LysoSensor indicated that intravacuolar organelles were strongly acidic and vacuoles were slightly acidic. This suggests that vacuolization is caused by accumulation of weak base and H(+) in acidic organelles, driven by vacuolar H(+)-ATPase associated with Cl(-) entering, and probably by subsequent extrusion of H(+) and water from organelles to the surrounding cytoplasm.

  9. Synthesis and antimicrobial activities of new higher amino acid Schiff base derivatives of 6-aminopenicillanic acid and 7-aminocephalosporanic acid

    NASA Astrophysics Data System (ADS)

    Özdemir (nee Güngör), Özlem; Gürkan, Perihan; Özçelik, Berrin; Oyardı, Özlem

    2016-02-01

    Novel β-lactam derivatives (1c-3c) (1d-3d) were produced by using 6-aminopenicillanic acid (6-APA), 7-aminocephalosporanic acid (7-ACA) and the higher amino acid Schiff bases. The synthesized compounds were characterized by elemental analysis, IR, 1H/13C NMR and UV-vis spectra. Antibacterial activities of all the higher amino acid Schiff bases (1a-3a) (1b-3b) and β-lactam derivatives were screened against three gram negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Acinetobacter baumannii RSKK 02026), three gram positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 07005, Bacillus subtilis ATCC 6633) and their drug-resistant isolates by using broth microdilution method. Two fungi (Candida albicans and Candida krusei) were used for antifungal activity.

  10. Acid-base homeostasis in the human system

    NASA Technical Reports Server (NTRS)

    White, R. J.

    1974-01-01

    Acid-base regulation is a cooperative phenomena in vivo with body fluids, extracellular and intracellular buffers, lungs, and kidneys all playing important roles. The present account is much too brief to be considered a review of present knowledge of these regulatory systems, and should be viewed, instead, as a guide to the elements necessary to construct a simple model of the mutual interactions of the acid-base regulatory systems of the body.

  11. Practical approach to physical-chemical acid-base management. Stewart at the bedside.

    PubMed

    Magder, Sheldon; Emami, Ali

    2015-01-01

    The late Peter Stewart developed an approach to the analysis of acid-base disturbances in biological systems based on basic physical-chemical principles. His key argument was that the traditional carbon dioxide/bicarbonate analysis with just the use of the Henderson-Hasselbalch equation does not account for the important role in the regulation of H(+) concentration played by strong ions, weak acids and water itself. Acceptance of his analysis has been limited because it requires a complicated set of calculations to account for all the variables and it does not provide simple clinical guidance. However, the analysis can be made more pragmatic by using a series of simple equations to quantify the major processes in acid-base disturbances. These include the traditional PCO2 component and the addition of four metabolic processes, which we classify as "water-effects," "chloride-effects," "albumin effects," and "others." Six values are required for the analysis: [Na(+)], [Cl(-)], pH, Pco2, albumin concentration, and base excess. The advantage of this approach is that it gives a better understanding of the mechanisms behind acid-base abnormalities and more readily leads to clinical actions that can prevent or correct the abnormalities. We have developed a simple free mobile app that can be used to input the necessary values to use this approach at the bedside (Physical/Chemical Acid Base Calculator).

  12. The central role of chloride in the metabolic acid-base changes in canine parvoviral enteritis.

    PubMed

    Burchell, Richard K; Schoeman, Johan P; Leisewitz, Andrew L

    2014-04-01

    The acid-base disturbances in canine parvoviral (CPV) enteritis are not well described. In addition, the mechanisms causing these perturbations have not been fully elucidated. The purpose of the present study was to assess acid-base changes in puppies suffering from CPV enteritis, using a modified strong ion model (SIM). The hypothesis of the study was that severe acid-base disturbances would be present and that the SIM would provide insights into pathological mechanisms, which have not been fully appreciated by the Henderson-Hasselbalch model. The study analysed retrospective data, obtained from 42 puppies with confirmed CPV enteritis and 10 healthy control dogs. The CPV-enteritis group had been allocated a clinical score, to allow classification of the data according to clinical severity. The effects of changes in free water, chloride, l-lactate, albumin and phosphate were calculated, using a modification of the base excess algorithm. When the data were summated for each patient, and correlated to each individual component, the most important contributor to the metabolic acid-base changes, according to the SIM, was chloride (P<0.001). Severely-affected animals tended to demonstrate hypochloraemic alkalosis, whereas mildly-affected puppies had a hyperchloraemic acidosis (P=0.007). In conclusion, the acid-base disturbances in CPV enteritis are multifactorial and complex, with the SIM providing information in terms of the origin of these changes.

  13. Fermi resonance and strong anharmonic effects in the absorption spectra of the ν-OH ( ν-OD) vibration of solid H- and D-benzoic acid

    NASA Astrophysics Data System (ADS)

    Yaremko, A. M.; Ratajczak, H.; Barnes, A. J.; Baran, J.; Durlak, P.; Latajka, Z.

    2009-10-01

    The vibrational spectra of polycrystalline benzoic acid (BA) and its deuterated derivative were studied over the wide frequency region 4000-10 cm -1 by IR and Raman methods. A theoretical analysis of the hydrogen bond frequency region and calculations at the B3LYP/6-311++G(2d, 2p) level for the benzoic acid cyclic dimer in the gas phase were made. In order to study the dynamics of proton transfer two formalisms were applied: Car-Parrinello Molecular Dynamics (CPMD) and Path Integrals Molecular Dynamics (PIMD). It was shown that the experimentally observed very broad ν-OH band absorption is the result of complex anharmonic interaction: Fermi resonance between the OH-stretching and bending vibrations and strong interaction of the ν-OH stretching with the low frequency phonons. The theoretical analysis in the framework of such an approach gave a good correlation with experiment. From the CPMD calculations it was confirmed that the O-H⋯O bridge is not rigid, with the O⋯O distance being described by a large amplitude motion. For the benzoic acid dimer we observed stepwise (asynchronous) proton transfer.

  14. Identification and quantification of the caproic acid-producing bacterium Clostridium kluyveri in the fermentation of pit mud used for Chinese strong-aroma type liquor production.

    PubMed

    Hu, Xiao-long; Du, Hai; Xu, Yan

    2015-12-01

    Chinese strong-aroma type liquor (CSAL) is a popular distilled alcoholic beverage in China. It is produced by a complex fermentation process that is conducted in pits in the ground. Ethyl caproate is a key flavor compound in CSAL and is thought to originate from caproic acid produced by Clostridia inhabiting the fermentation pit mud. However, the particular species of Clostridium associated with this production are poorly understood and problematic to quantify by culturing. In this study, a total of 28 closest relatives including 15 Clostridia and 8 Bacilli species in pit muds from three CSAL distilleries, were detected by culture-dependent and -independent methods. Among them, Clostridium kluyveri was identified as the main producer of caproic acid. One representative strain C. kluyveri N6 could produce caproic, butyric and octanoic acids and their corresponding ethyl esters, contributing significantly to CSAL flavor. A real time quantitative PCR assay of C. kluyveri in pit muds developed showed that a concentration of 1.79×10(7) 16S rRNA gene copies/g pit mud in LZ-old pit was approximately six times higher than that in HLM and YH pits and sixty times higher than that in LZ-new pit respectively. This method can be used to improve the management of pit mud microbiology and its impact on CSAL quality. PMID:26267890

  15. Vinylbenzyl quaternary ammonium-based polymeric monolith with hydrophilic interaction/strong anion exchange mixed-mode for pressurized capillary electrochromatography.

    PubMed

    Lin, Xucong; Feng, Shuhui; Jia, Wenchao; Ding, Kang; Xie, Zenghong

    2013-11-01

    A novel polymeric monolith with hydrophilic interaction and strong anion-exchange mixed-mode has been fabricated for pressurized capillary electrochromatography by an in situ copolymerization of vinylbenzyl trimethylammonium chloride (VBTA) and bisphenol A glycerolate dimethacrylate (BisGMA). The optimization of the polymerization mixture composition has been investigated, and column characteristics in terms of mechanical stability, permeability and reproducibility have been studied in detail. Linear responses between back pressure and flow rate have been achieved in different solvents. The absolute value of swelling propensity (SP) factor for poly(VBTA-co-BisGMA) monolith is 0.41, and the degree of permeability drop from pure ACN to water is about 45%. An acceptable mechanical stability of the column is obtained. The suitable reproducibility is also measured with the RSD for day-to-day (n=3) of retention time and column efficiency less than 3.3%, and the RSD for batch-to-batch (n=3) less than 5.3%, respectively. Under the optimum conditions, the mixed-mode of hydrophilic interaction and strong anion-exchange has been carried out, and efficient electrochromatography profiling of various polar compounds including neutral phenols, negatively charged benzoic acids and positively charged nucleic acid bases and nucleosides are achieved, respectively. PMID:24125728

  16. A Diffusion Approximation Based on Renewal Processes with Applications to Strongly Biased Run-Tumble Motion.

    PubMed

    Thygesen, Uffe Høgsbro

    2016-03-01

    We consider organisms which use a renewal strategy such as run-tumble when moving in space, for example to perform chemotaxis in chemical gradients. We derive a diffusion approximation for the motion, applying a central limit theorem due to Anscombe for renewal-reward processes; this theorem has not previously been applied in this context. Our results extend previous work, which has established the mean drift but not the diffusivity. For a classical model of tumble rates applied to chemotaxis, we find that the resulting chemotactic drift saturates to the swimming velocity of the organism when the chemical gradients grow increasingly steep. The dispersal becomes anisotropic in steep gradients, with larger dispersal across the gradient than along the gradient. In contrast to one-dimensional settings, strong bias increases dispersal. We next include Brownian rotation in the model and find that, in limit of high chemotactic sensitivity, the chemotactic drift is 64% of the swimming velocity, independent of the magnitude of the Brownian rotation. We finally derive characteristic timescales of the motion that can be used to assess whether the diffusion limit is justified in a given situation. The proposed technique for obtaining diffusion approximations is conceptually and computationally simple, and applicable also when statistics of the motion is obtained empirically or through Monte Carlo simulation of the motion. PMID:27012850

  17. Confined surface plasmon sensors based on strongly coupled disk-in-volcano arrays.

    PubMed

    Ai, Bin; Wang, Limin; Möhwald, Helmuth; Yu, Ye; Zhang, Gang

    2015-02-14

    Disk-in-volcano arrays are reported to greatly enhance the sensing performance due to strong coupling in the nanogaps between the nanovolcanos and nanodisks. The designed structure, which is composed of a nanovolcano array film and a disk in each cavity, is fabricated by a simple and efficient colloidal lithography method. By tuning structural parameters, the disk-in-volcano arrays show greatly enhanced resonances in the nanogaps formed by the disks and the inner wall of the volcanos. Therefore they respond to the surrounding environment with a sensitivity as high as 977 nm per RIU and with excellent linear dependence on the refraction index. Moreover, through mastering the fabrication process, biological sensing can be easily confined to the cavities of the nanovolcanos. The local responsivity has the advantages of maximum surface plasmon energy density in the nanogaps, reducing the sensing background and saving expensive reagents. The disk-in-volcano arrays also possess great potential in applications of optical and electrical trapping and single-molecule analysis, because they enable establishment of electric fields across the gaps.

  18. Confined surface plasmon sensors based on strongly coupled disk-in-volcano arrays.

    PubMed

    Ai, Bin; Wang, Limin; Möhwald, Helmuth; Yu, Ye; Zhang, Gang

    2015-02-14

    Disk-in-volcano arrays are reported to greatly enhance the sensing performance due to strong coupling in the nanogaps between the nanovolcanos and nanodisks. The designed structure, which is composed of a nanovolcano array film and a disk in each cavity, is fabricated by a simple and efficient colloidal lithography method. By tuning structural parameters, the disk-in-volcano arrays show greatly enhanced resonances in the nanogaps formed by the disks and the inner wall of the volcanos. Therefore they respond to the surrounding environment with a sensitivity as high as 977 nm per RIU and with excellent linear dependence on the refraction index. Moreover, through mastering the fabrication process, biological sensing can be easily confined to the cavities of the nanovolcanos. The local responsivity has the advantages of maximum surface plasmon energy density in the nanogaps, reducing the sensing background and saving expensive reagents. The disk-in-volcano arrays also possess great potential in applications of optical and electrical trapping and single-molecule analysis, because they enable establishment of electric fields across the gaps. PMID:25384425

  19. Acid Base Titrations in Nonaqueous Solvents and Solvent Mixtures

    NASA Astrophysics Data System (ADS)

    Barcza, Lajos; Buvári-Barcza, Ágnes

    2003-07-01

    The acid base determination of different substances by nonaqueous titrations is highly preferred in pharmaceutical analyses since the method is quantitative, exact, and reproducible. The modern interpretation of the reactions in nonaqueous solvents started in the last century, but several inconsistencies and unsolved problems can be found in the literature. The acid base theories of Brønsted Lowry and Lewis as well as the so-called solvent theory are outlined first, then the promoting (and leveling) and the differentiating effects are discussed on the basis of the hydrogen-bond concept. Emphasis is put on the properties of formic acid and acetic anhydride since their importance is increasing.

  20. Carbonic anhydrase and acid-base regulation in fish.

    PubMed

    Gilmour, K M; Perry, S F

    2009-06-01

    Carbonic anhydrase (CA) is the zinc metalloenzyme that catalyses the reversible reactions of CO(2) with water. CA plays a crucial role in systemic acid-base regulation in fish by providing acid-base equivalents for exchange with the environment. Unlike air-breathing vertebrates, which frequently utilize alterations of breathing (respiratory compensation) to regulate acid-base status, acid-base balance in fish relies almost entirely upon the direct exchange of acid-base equivalents with the environment (metabolic compensation). The gill is the critical site of metabolic compensation, with the kidney playing a supporting role. At the gill, cytosolic CA catalyses the hydration of CO(2) to H(+) and HCO(3)(-) for export to the water. In the kidney, cytosolic and membrane-bound CA isoforms have been implicated in HCO(3)(-) reabsorption and urine acidification. In this review, the CA isoforms that have been identified to date in fish will be discussed together with their tissue localizations and roles in systemic acid-base regulation.

  1. Characterisation of acid-base abnormalities in pigs experimentally infected with Chlamydia suis.

    PubMed

    Reinhold, Petra; Hartmann, Helmut; Constable, Peter D

    2010-05-01

    This study characterises the acid-base abnormalities in pigs experimentally infected with Chlamydia suis (Henderson-Hasselbalch equation and Constable's simplified strong ion equation). Eight pigs were challenged with the respiratory pathogen C. suis and four pigs served as non-infected controls. Pigs were monitored from 7 days before challenge to 8 days post-inoculation. Clinical examination was performed twice daily and venous blood samples were collected every two days. Blood-gas analysis, haemoxymetry, serum biochemical analysis and electrophoresis were performed in order to characterise the acid-base derangement. Aerosol challenge with C. suis resulted in severe acid-base disturbance characterised by acute respiratory acidosis and strong ion (metabolic) acidosis secondary to anaerobic metabolism and hyper L-lactataemia. Maximal changes were seen at day 3 post-inoculation when severe clinical signs of respiratory dysfunction were evident. The results of the study provide new information regarding the pathophysiology of respiratory infection caused by C. suis and the applicability and diagnostic utility of different approaches for assessing acid-base status in pigs.

  2. Strong Interaction

    SciTech Connect

    Karsch, F.; Vogelsang, V.

    2009-09-29

    We will give here an overview of our theory of the strong interactions, Quantum Chromo Dynamics (QCD) and its properties. We will also briefly review the history of the study of the strong interactions, and the discoveries that ultimately led to the formulation of QCD. The strong force is one of the four known fundamental forces in nature, the others being the electromagnetic, the weak and the gravitational force. The strong force, usually referred to by scientists as the 'strong interaction', is relevant at the subatomic level, where it is responsible for the binding of protons and neutrons to atomic nuclei. To do this, it must overcome the electric repulsion between the protons in an atomic nucleus and be the most powerful force over distances of a few fm (1fm=1 femtometer=1 fermi=10{sup -15}m), the typical size of a nucleus. This property gave the strong force its name.

  3. Composition of exchangeable bases and acidity in soils of the Crimean Mountains

    NASA Astrophysics Data System (ADS)

    Kostenko, I. V.

    2015-08-01

    Acid forest and mountainous meadow soils of the Crimean Mountains were studied. The amount of hydrogen and aluminum ions extracted from these soils depended on the pH of extracting agents. The maximum values of the soil acidity were obtained upon the extraction with a strongly alkaline solution of sodium acetate in 0.05 N NaOH. The application of this extractant made it possible to determine the total exchange acidity, the total amount of extractable aluminum, and the total cation exchange capacity of the soils after the extraction of all the acidic components from them. The values of these characteristics were significantly higher than the values of the potential acidity and cation exchange capacity obtained by the routine analytical methods. Hydrogen predominated among the acidic components of the exchange acidity in the humus horizons, whereas aluminum predominated among them in the underlying mineral horizons. Hydrothermic conditions and the character of vegetation and parent materials were the major factors affecting the relationships between bases and acidic components in the soil adsorption complex.

  4. An Acid-Base Chemistry Example: Conversion of Nicotine

    NASA Astrophysics Data System (ADS)

    Summerfield, John H.

    1999-10-01

    The current government interest in nicotine conversion by cigarette companies provides an example of acid-base chemistry that can be explained to students in the second semester of general chemistry. In particular, the conversion by ammonia of the +1 form of nicotine to the easier-to-assimilate free-base form illustrates the effect of pH on acid-base equilibrium. The part played by ammonia in tobacco smoke is analogous to what takes place when cocaine is "free-based".

  5. Strong Optomechanical Coupling in Nanobeam Cavities based on Hetero Optomechanical Crystals

    PubMed Central

    Huang, Zhilei; Cui, Kaiyu; Li, Yongzhuo; Feng, Xue; Liu, Fang; Zhang, Wei; Huang, Yidong

    2015-01-01

    Nanobeam cavities based on hetero optomechanical crystals are proposed. With optical and mechanical modes separately confined by two types of periodic structures, the mechanical frequency is designed as high as 5.88 GHz. Due to the optical field and the strain field concentrated in the optomechanical cavity and resembling each other with an enhanced overlap, a high optomechanical coupling rate of 1.31 MHz is predicted. PMID:26530128

  6. Strong and Robust Polyaniline-Based Supramolecular Hydrogels for Flexible Supercapacitors.

    PubMed

    Li, Wanwan; Gao, Fengxian; Wang, Xiaoqian; Zhang, Ning; Ma, Mingming

    2016-08-01

    We report a supramolecular strategy to prepare conductive hydrogels with outstanding mechanical and electrochemical properties, which are utilized for flexible solid-state supercapacitors (SCs) with high performance. The supramolecular assembly of polyaniline and polyvinyl alcohol through dynamic boronate bond yields the polyaniline-polyvinyl alcohol hydrogel (PPH), which shows remarkable tensile strength (5.3 MPa) and electrochemical capacitance (928 F g(-1) ). The flexible solid-state supercapacitor based on PPH provides a large capacitance (306 mF cm(-2) and 153 F g(-1) ) and a high energy density of 13.6 Wh kg(-1) , superior to other flexible supercapacitors. The robustness of the PPH-based supercapacitor is demonstrated by the 100 % capacitance retention after 1000 mechanical folding cycles, and the 90 % capacitance retention after 1000 galvanostatic charge-discharge cycles. The high activity and robustness enable the PPH-based supercapacitor as a promising power device for flexible electronics. PMID:27328742

  7. Arsenic Exposure and Cancer Mortality in a US-based Prospective Cohort: the Strong Heart Study

    PubMed Central

    García-Esquinas, Esther; Pollán, Marina; Umans, Jason G.; Francesconi, Kevin A.; Goessler, Walter; Guallar, Eliseo; Howard, Barbara; Farley, John; Yeh, Jeunliang; Best, Lyle G.; Navas-Acien, Ana

    2013-01-01

    Background Inorganic arsenic, a carcinogen at high exposure levels, is a major global health problem. Prospective studies on carcinogenic effects at low-moderate arsenic levels are lacking. Methods We evaluated the association between baseline arsenic exposure and cancer mortality in 3,932 American Indians 45–74 years from Arizona, Oklahoma and North/South Dakota who participated in the Strong Heart Study in 1989–1991 and were followed through 2008. We estimated inorganic arsenic exposure as the sum of inorganic and methylated species in urine. Cancer deaths (386 overall, 78 lung, 34 liver, 18 prostate, 26 kidney, 24 esophagus/stomach, 25 pancreas, 32 colon/rectal, 26 breast, 40 lymphatic/hematopoietic) were assessed by mortality surveillance reviews. We hypothesized an association with lung, liver, prostate and kidney cancer. Results Median (interquartile range) urine concentration for inorganic plus methylated arsenic species was 9.7 (5.8–15.6) μg/g creatinine. The adjusted hazard ratios (95% CI) comparing the 80th versus 20th percentiles of arsenic were 1.14 (0.92–1.41) for overall cancer, 1.56 (1.02–2.39) for lung cancer, 1.34 (0.66, 2.72) for liver cancer, 3.30 (1.28–8.48) for prostate cancer, and 0.44 (0.14, 1.14) for kidney cancer. The corresponding hazard ratios were 2.46 (1.09–5.58) for pancreatic cancer, and 0.46 (0.22–0.96) for lymphatic and hematopoietic cancers. Arsenic was not associated with cancers of the esophagus and stomach, colon and rectum, and breast. Conclusions Low to moderate exposure to inorganic arsenic was prospectively associated with increased mortality for cancers of the lung, prostate and pancreas. Impact These findings support the role of low-moderate arsenic exposure in lung, prostate and pancreas cancer development and can inform arsenic risk assessment. PMID:23800676

  8. Studies on the acid-base properties of the AIBr sub 3 -NaBr melts

    SciTech Connect

    Hayashi, H. ); Hayashi, N.; Takehara, Z. ); Katagiri, A. )

    1989-09-01

    Recently, a lot of work has been performed on the acid-base properties of Lewis acidic molten salts. One of the most extensively investigated melt systems is the sodium chloroaluminate melt (175{degrees}-220{degrees}C) in which the chloride ion activity is dependent upon the composition of the melt. It is well known that unusual higher oxidation state ionic species, such as S(IV) or lower oxidation state cluster compounds, such as W{sub 6}CI{sub 8}{sup 4 +}, can be stable in the chloroaluminate melts because of the strong Lewis acidity of these solvents. These melts are now one of the potential solvents. These melts are now one of the potential materials for use in low-temperature molten salt batteries or as solvents for organic syntheses. The aluminum bromide-sodium bromide melts also show the variable Lewis acidity. Some physical properties of the haloaluminate melts are dependent on the halide species. Therefore, the acid-base properties of the melts also may vary with the anion component, even with the same cationic constituent. The authors discuss how they investigated the acid-base properties of the AIBr{sub 3}-NaBr melts and compared their characteristics with those of the chloroaluminate melts.

  9. Nationwide Registry-Based Analysis of Cancer Clustering Detects Strong Familial Occurrence of Kaposi Sarcoma

    PubMed Central

    Vahteristo, Pia; Patama, Toni; Li, Yilong; Saarinen, Silva; Kilpivaara, Outi; Pitkänen, Esa; Knekt, Paul; Laaksonen, Maarit; Artama, Miia; Lehtonen, Rainer; Aaltonen, Lauri A.; Pukkala, Eero

    2013-01-01

    Many cancer predisposition syndromes are rare or have incomplete penetrance, and traditional epidemiological tools are not well suited for their detection. Here we have used an approach that employs the entire population based data in the Finnish Cancer Registry (FCR) for analyzing familial aggregation of all types of cancer, in order to find evidence for previously unrecognized cancer susceptibility conditions. We performed a systematic clustering of 878,593 patients in FCR based on family name at birth, municipality of birth, and tumor type, diagnosed between years 1952 and 2011. We also estimated the familial occurrence of the tumor types using cluster score that reflects the proportion of patients belonging to the most significant clusters compared to all patients in Finland. The clustering effort identified 25,910 birth name-municipality based clusters representing 183 different tumor types characterized by topography and morphology. We produced information about familial occurrence of hundreds of tumor types, and many of the tumor types with high cluster score represented known cancer syndromes. Unexpectedly, Kaposi sarcoma (KS) also produced a very high score (cluster score 1.91, p-value <0.0001). We verified from population records that many of the KS patients forming the clusters were indeed close relatives, and identified one family with five affected individuals in two generations and several families with two first degree relatives. Our approach is unique in enabling systematic examination of a national epidemiological database to derive evidence of aberrant familial aggregation of all tumor types, both common and rare. It allowed effortless identification of families displaying features of both known as well as potentially novel cancer predisposition conditions, including striking familial aggregation of KS. Further work with high-throughput methods should elucidate the molecular basis of the potentially novel predisposition conditions found in this

  10. Strong field enhancement and light-matter interactions with all-dielectric metamaterials based on split bar resonators.

    PubMed

    Zhang, Jianfa; Liu, Wei; Zhu, Zhihong; Yuan, Xiaodong; Qin, Shiqiao

    2014-12-15

    Strong subwavelength field enhancement has often been assumed to be unique to plasmonic nanostructures. Here we propose a type of all-dielectric metamaterials based on split bar resonators. The nano gap at the centre of the resonant elements results in large local field enhancement and light localization in the surrounding medium, which can be employed for strong light-matter interactions. In a Fano-resonant dielectric metamaterial comprising pairs of asymmetric split silicon bars, the enhancement of electric field amplitude in the gap exceeds 120 while the averaged electromagnetic energy density is enhanced by more than 7000 times. An optical refractive index sensor with a potential sensitivity of 525 nm/RIU is designed based on the proposed metamaterials. The proposed concept can be applied to other types of dielectric nanostructures and may stimulate further research of dielectric metamaterials for applications ranging from nonlinear optics and sensing to the realization of new types of active lasing devices.

  11. Development of tough, strong, iron-base alloy for cryogenic applications

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1983-01-01

    The development of an iron-base alloy that combines the normally divergent properties of high toughness and high strength at cryogenic temperatures is discussed. Specifically, alloy properties were sought which at -196 C would exhibit a fracture toughness of 220 MPa-m(1/2) with a corresponding yield strength of 1.4 GPa (200 ksi). Early work showed that high toughness could be achieved in Fe-12Ni alloys containing reactive metal additions such as Al, Nb, Ti, and V. Further research emphasized strengthening of these tough alloys by thermomechanical processing and the addition of Cu. Results showed that high strength and high toughness could be achieved in a single alloy at temperatures as low as -196 C. An alloy with composition Fe-12Ni-9.5Al-2Cu exhibited a yield strength of 1.65 GPa with a corresponding fracture toughness of 220 MPa-m(1/2) at -196 C. Strengthening due to Cu additions to the Fe-12Ni base alloys results primarily from precipitation of Cu-rich epsilon particles approximately 20 nm in diameter. Strengthening mechanisms are discussed in terms of an elastic modulus hardening model and are supported by transimission electron microscopy examinations of selected test specimens.

  12. Roles of urea production, ammonium excretion, and amino acid oxidation in acid-base balance.

    PubMed

    Mackenzie, W

    1986-02-01

    Atkinson and colleagues recently proposed several concepts that contrast with traditional views: first, that acid-base balance is regulated chiefly by the reactions leading to urea production in the liver; second, that ammonium excretion by the kidney plays no role in acid-base homeostasis; and third, that ammonium does not stimulate ureagenesis (except indirectly). To examine these concepts, plasma ions other than bicarbonate are categorized as 1) fixed cations (Na+, K+, Ca2+, and Mg2+, symbolized M+) and anions (Cl-), 2) buffer anions (A-), 3) other anions (X-), and 4) ammonium plus charged amino groups (N+). Since electroneutrality dictates that M+ + N+ = Cl- + HCO3- + A- + X-, it follows that delta HCO3- = delta(M+ - Cl-) - delta A- - delta X- + delta N+. Therefore acid-base disturbances (changes in HCO3-) can be categorized as to how they affect bodily content and hence plasma concentration of each of these four types of ions. The stoichiometry of ureagenesis, glutamine hydrolysis, ammonium and titratable acid excretion, oxidation of neutral, acidic, and basic amino acids, and oxidation of methionine, phosphoserine, and protein are examined to see how they alter these quantities. It is concluded that 1) although ureagenesis is pH dependent and also counteracts a tendency of amino acid oxidation to cause alkalosis, this tendency is inherently limited by the hyperammonemia (delta N+) that necessarily accompanies it, 2) ammonium excretion is equivalent to hydrogen excretion in its effects on acid-base balance if, and only if, it occurs in exchange for sodium or is accompanied by chloride excretion and only when the glutamate generated by glutamine hydrolysis is oxidized.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3511732

  13. A model for strong interactions at high energy based on the CGC/saturation approach

    NASA Astrophysics Data System (ADS)

    Gotsman, E.; Levin, E.; Maor, U.

    2015-01-01

    We present our first attempt to develop a model for soft interactions at high energy, based on the BFKL Pomeron and the CGC/saturation approach. We construct an eikonal-type model, whose opacity is determined by the exchange of the dressed BFKL Pomeron. The Green function of the Pomeron is calculated in the framework of the CGC/saturation approach. Using five parameters we achieve a reasonable description of the experimental data at high energies ( TeV) with overall . The model results in different behavior for the single- and double-diffraction cross sections at high energies. The single-diffraction cross section reaches a saturated value (about 10 mb) at high energies, while the double-diffraction cross section continues growing slowly.

  14. Strong and broadband terahertz absorber using SiO2-based metamaterial structure

    NASA Astrophysics Data System (ADS)

    Mo, Man-Man; Wen, Qi-Ye; Chen, Zhi; Yang, Qing-Hui; Qiu, Dong-Hong; Li, Sheng; Jing, Yu-Lan; Zhang, Huai-Wu

    2014-04-01

    We design and experimentally demonstrate a broadband metamaterial absorber in the terahertz (THz) band based on a periodic array of aluminum (Al) squares with two different sizes. A thin silicon dioxide (SiO2) film rather than a conventional polyimide (PI) layer is used as a dielectric spacer to separate Al squares from the platinum (Pt) ground plane in our design, which significantly improves the design precision and the feasibility of the device fabrication. The combination of different sizes of Al squares gives rise to an absorption bandwidth of over 210 GHz with an absorption of over 90%. Our results also show that our device is almost polarization-insensitive. It works very well for all azimuthal angles with an absorption of beyond 80%.

  15. Light-driven strong spin valve effects in an azobenzene-based spin optoelectronic device

    NASA Astrophysics Data System (ADS)

    Zeng, Jing; Chen, Ke-Qiu; Deng, Xiaohui; Long, Mengqiu

    2016-10-01

    A photoswitched single-molecule junction, a stable and reversible single-molecule electrical switch, has been successfully prepared by means of molecular engineering (2016 Science 352 1443). In this work we use a first-principles computational approach to investigate the spin valve effect of an azobenzene-based spin optoelectronic device. Our results demonstrate that the magnetoresistive ratio of the spin optoelectronic device is only about 65% when the azobenzene is in cis configuration, which is a low performance for practical applications. However, the magnetoresistive ratio of the device can be enhanced to about 2775% when the cis configuration of the azobenzene is changed into the trans configuration by applying a pulse of light. As a consequence, photoexcitation provides an effective way to obtain a high-performance spin optoelectronic device.

  16. Two-temperature Models for Polar Plumes: Cooling by Means of Strong Base Heating

    NASA Astrophysics Data System (ADS)

    Grappin, R.; Wang, Y.-M.; Pantellini, F.

    2011-01-01

    In earlier one-fluid hydrodynamical calculations incorporating heat conduction and radiative losses, it was shown that the high densities in polar plumes could be reproduced by including a concentrated heat source near the plume base, in addition to the global heating required in both the plume and interplume regions of the coronal hole. The extra heating (attributed to interchange reconnection between the open flux and an underlying magnetic bipole) results in lower flow speeds and temperatures relative to the interplume gas, predictions that have since been confirmed by spectroscopic measurements. Here, the model is extended to the two-fluid case, in which ions and electrons are allowed to have different temperatures, coupling is via Coulomb collisions, and heat transport is mainly by electrons. Again, we find that depositing energy very close to the coronal base, in either the protons or electrons (or both), raises the densities and decreases the flow speeds everywhere along the flux tube. The higher densities in turn act to lower the ion temperatures by coupling the protons more closely to the energy-losing electrons. In addition, we find that energy must be deposited globally in both the electrons and the ions; without this direct heating, the electrons would end up cooler in the interplume region than in the plume, contrary to observations. Increasing the rate of flux-tube expansion has the effect of lowering the electron and ion temperatures and reducing the asymptotic flow speed, both in the plume and the interplume region; the observed densities and temperatures can be matched by taking the magnetic field to fall off with radius roughly as r -4.

  17. Equivalence-point electromigration acid-base titration via moving neutralization boundary electrophoresis.

    PubMed

    Yang, Qing; Fan, Liu-Yin; Huang, Shan-Sheng; Zhang, Wei; Cao, Cheng-Xi

    2011-04-01

    In this paper, we developed a novel method of acid-base titration, viz. the electromigration acid-base titration (EABT), via a moving neutralization boundary (MNR). With HCl and NaOH as the model strong acid and base, respectively, we conducted the experiments on the EABT via the method of moving neutralization boundary for the first time. The experiments revealed that (i) the concentration of agarose gel, the voltage used and the content of background electrolyte (KCl) had evident influence on the boundary movement; (ii) the movement length was a function of the running time under the constant acid and base concentrations; and (iii) there was a good linearity between the length and natural logarithmic concentration of HCl under the optimized conditions, and the linearity could be used to detect the concentration of acid. The experiments further manifested that (i) the RSD values of intra-day and inter-day runs were less than 1.59 and 3.76%, respectively, indicating similar precision and stability in capillary electrophoresis or HPLC; (ii) the indicators with different pK(a) values had no obvious effect on EABT, distinguishing strong influence on the judgment of equivalence-point titration in the classic one; and (iii) the constant equivalence-point titration always existed in the EABT, rather than the classic volumetric analysis. Additionally, the EABT could be put to good use for the determination of actual acid concentrations. The experimental results achieved herein showed a new general guidance for the development of classic volumetric analysis and element (e.g. nitrogen) content analysis in protein chemistry.

  18. Role of acids and bases in nanoparticle growth

    NASA Astrophysics Data System (ADS)

    Yli-Juuti, Taina; Barsanti, Kelley; Bzdek, Bryan; Hildebrandt Ruiz, Lea; Jokinen, Tuija; Kieloaho, Antti-Jussi; Makkonen, Ulla; Petäjä, Tuukka; Ruuskanen, Taina; Johnston, Murray; Kulmala, Markku; Riipinen, Ilona

    2014-05-01

    Secondary aerosol particles that are formed in atmosphere by gas-to-particle conversion during new particle formation events have potential to affect climate significantly due to their typically high number concentrations. This, however, requires that the freshly formed nanoparticles of about 1 nm in diameter grow tens of nanometers and reach climatically relevant sizes, i.e. sizes where they can act as cloud condensation nuclei. During the growth towards larger sizes the nanoparticles are subject to coagulational losses, and the rate at which the nanoparticles grow by condensation of vapors is a key factor affecting their probability to survive to climatically relevant sizes. Vapors that condense on the nanoparticles can be produced in the atmosphere from volatile compounds through gas phase chemical reactions, and their volatility can also be further lowered by particle phase processes. Therefore, particle composition and particle phase processes may influence nanoparticle growth. We study the growth of atmospheric nanoparticles and especially the role of particle phase salt formation in the nanoparticle growth using MABNAG model (Model for Acid-Base chemistry in NAnoparticle Growth) and by comparing to atmospheric measurements. MABNAG is a condensation growth model for aqueous solution particles. In MABNAG the dynamics of gas phase mass transport of vapors to particle are coupled with thermodynamics of particle phase acid-base chemistry, and both the composition and size dependence of equilibrium vapor pressures are accounted for. The model is applied especially for boreal forest environment. Here nanoparticle growth is modeled with a system of water, two acids (sulfuric acid and an organic acid) and two bases (ammonia and an amine) as condensing vapors. Focus is on the neutralization of acids by the bases and the related effects on the particle growth. According to the model predictions the enhancement of condensation of organic acid due to salt formation is

  19. Stability of polydopamine and poly(DOPA) melanin-like films on the surface of polymer membranes under strongly acidic and alkaline conditions.

    PubMed

    Wei, Houliang; Ren, Jun; Han, Bo; Xu, Li; Han, Lulu; Jia, Lingyun

    2013-10-01

    This study investigated the stability of polydopamine and poly(3,4-dihydroxyphenylalanine) (poly(DOPA)) melanin-like films on the surface of polymer substrates. Three polymer membranes, polypropylene (PP), poly(vinylidenefluoride) (PVDF) and nylon, were modified with polydopamine or poly(DOPA), and then immersed in 0.1M HCl or NaOH, followed by UV-vis spectrometry analysis to detect the presence of film detachment. The results showed that the outer parts of both polydopamine and poly(DOPA) films were detached, probably due to electrostatic repulsion between the polymers within the film, when the modified membranes were washed in HCl or NaOH solution. These two films were more stable in strongly acidic solution, but the stability of poly(DOPA) film was better than that of polydopamine film. Compared to the films on the surface of PVDF or nylon membrane, films on PP surface showed the lowest stability, possibly because of the hydrophobic property of PP. The process of film detachment was analyzed by GPC, which showed that unreacted dopamine or DOPA monomers were still present in the freshly formed films. The unreacted monomers, as well as polydopamine or poly(DOPA) that were incorporated in the film via noncovalent interactions, became detached when the film was exposed to strongly acidic or alkaline solution. Oxidation of freshly formed films could significantly enhance their stability. The results therefore provide us with a better understanding of the stability of melanin-like films, and allow us to develop an effective strategy for constructing stable films. PMID:23707846

  20. Poly (ricinoleic acid) based novel thermosetting elastomer.

    PubMed

    Ebata, Hiroki; Yasuda, Mayumi; Toshima, Kazunobu; Matsumura, Shuichi

    2008-01-01

    A novel bio-based thermosetting elastomer was prepared by the lipase-catalyzed polymerization of methyl ricinoleate with subsequent vulcanization. Some mechanical properties of the cured carbon black-filled polyricinoleate compounds were evaluated as a thermosetting elastomer. It was found that the carbon black-filled polyricinoleate compounds were readily cured by sulfur curatives to produce a thermosetting elastomer that formed a rubber-like sheet with a smooth and non-sticky surface. The curing behaviors and mechanical properties were dependent on both the molecular weight of the polyricinoleate and the amount of the sulfur curatives. Cured compounds consisting of polyricinoleate with a molecular weight of 100,800 showed good mechanical properties, such as a hardness of 48 A based on the durometer A measurements, a tensile strength at break of 6.91 MPa and an elongation at break of 350%. PMID:18469493

  1. The role of acid-base imbalance in statin-induced myotoxicity.

    PubMed

    Taha, Dhiaa A; De Moor, Cornelia H; Barrett, David A; Lee, Jong Bong; Gandhi, Raj D; Hoo, Chee Wei; Gershkovich, Pavel

    2016-08-01

    Disturbances in acid-base balance, such as acidosis and alkalosis, have potential to alter the pharmacologic and toxicologic outcomes of statin therapy. Statins are commonly prescribed for elderly patients who have multiple comorbidities such as diabetes mellitus, cardiovascular, and renal diseases. These patients are at risk of developing acid-base imbalance. In the present study, the effect of disturbances in acid-base balance on the interconversion of simvastatin and pravastatin between lactone and hydroxy acid forms have been investigated in physiological buffers, human plasma, and cell culture medium over pH ranging from 6.8-7.8. The effects of such interconversion on cellular uptake and myotoxicity of statins were assessed in vitro using C2C12 skeletal muscle cells under conditions relevant to acidosis, alkalosis, and physiological pH. Results indicate that the conversion of the lactone forms of simvastatin and pravastatin to the corresponding hydroxy acid is strongly pH dependent. At physiological and alkaline pH, substantial proportions of simvastatin lactone (SVL; ∼87% and 99%, respectively) and pravastatin lactone (PVL; ∼98% and 99%, respectively) were converted to the active hydroxy acid forms after 24 hours of incubation at 37°C. At acidic pH, conversion occurs to a lower extent, resulting in greater proportion of statin remaining in the more lipophilic lactone form. However, pH alteration did not influence the conversion of the hydroxy acid forms of simvastatin and pravastatin to the corresponding lactones. Furthermore, acidosis has been shown to hinder the metabolism of the lactone form of statins by inhibiting hepatic microsomal enzyme activities. Lipophilic SVL was found to be more cytotoxic to undifferentiated and differentiated skeletal muscle cells compared with more hydrophilic simvastatin hydroxy acid, PVL, and pravastatin hydroxy acid. Enhanced cytotoxicity of statins was observed under acidic conditions and is attributed to increased

  2. Metamaterial-based gradient index lens with strong focusing in the THz frequency range.

    PubMed

    Neu, J; Krolla, B; Paul, O; Reinhard, B; Beigang, R; Rahm, M

    2010-12-20

    The development of innovative terahertz (THz) imaging systems has recently moved in the focus of scientific efforts due to the ability to screen substances through textiles or plastics. The invention of THz imaging systems with high spatial resolution is of increasing interest for applications in the realms of quality control, spectroscopy in dusty environment and security inspections. To realize compact THz imaging systems with high spatial resolution it is necessary to develop lenses of minimized thickness that still allow one to focus THz radiation to small spot diameters with low optical aberrations. In addition, it would be desirable if the lenses offered adaptive control of their optical properties to optimize the performance of the imaging systems in the context of different applications. Here we present the design, fabrication and the measurement of the optical properties of spectrally broadband metamaterial-based gradient index (GRIN) lenses that allow one to focus THz radiation to a spot diameter of approximately one wavelength. Due to the subwavelength thickness and the high focusing strength the presented GRIN lenses are an important step towards compact THz imaging systems with high spatial resolution. Furthermore, the results open the path to a new class of adaptive THz optics by extension of the concept to tunable metamaterials. PMID:21197049

  3. Mechanically strong triple network hydrogels based on hyaluronan and poly(N,N-dimethylacrylamide).

    PubMed

    Tavsanli, Burak; Can, Volkan; Okay, Oguz

    2015-11-21

    Hyaluronan (HA) is a natural polyelectrolyte with distinctive biological functions. Cross-linking of HA to generate less degradable hydrogels for use in biomedical applications has attracted interest over many years. One limitation of HA hydrogels is that they are very brittle and/or easily dissolve in physiological environments, which limit their use in load-bearing applications. Herein, we describe the preparation of triple-network (TN) hydrogels based on HA and poly(N,N-dimethylacrylamide) (PDMA) of high mechanical strength by sequential gelation reactions. TN hydrogels containing 81-91% water sustain compressive stresses above 20 MPa and exhibit Young's moduli of up to 1 MPa. HA of various degrees of methacrylation was used as a multifunctional macromer for the synthesis of the brittle first-network component, while loosely cross-linked PDMA was used as the ductile, second and third network components of TN hydrogels. By tuning the methacrylation degree of HA, double-network hydrogels with a fracture stress above 10 MPa and a fracture strain of 96% were obtained. Increasing the ratio of ductile-to-brittle components via the TN approach further increases the fracture stress above 20 MPa. Cyclic mechanical tests show that, although TN hydrogels internally fracture even under small strain, the ductile components hinder macroscopic crack propagation by keeping the macroscopic gel samples together.

  4. Sulfuric acid nucleation: An experimental study of the effect of seven bases

    NASA Astrophysics Data System (ADS)

    Glasoe, W. A.; Volz, K.; Panta, B.; Freshour, N.; Bachman, R.; Hanson, D. R.; McMurry, P. H.; Jen, C.

    2015-03-01

    Nucleation of particles with sulfuric acid, water, and nitrogeneous bases was studied in a flow reactor. Sulfuric acid and water levels were set by flows over sulfuric acid and water reservoirs, respectively, and the base concentrations were determined from measured permeation rates and flow dilution ratios. Particle number distributions were measured with a nano-differential-mobility-analyzer system. Results indicate that the nucleation capability of NH3, methylamine, dimethylamine, and trimethylamine with sulfuric acid increases from NH3 as the weakest, methylamine next, and dimethylamine and trimethylamine the strongest. Three other bases were studied, and experiments with triethylamine showed that it is less effective than methylamine, and experiments with urea and acetamide showed that their capabilities are much lower than the amines with acetamide having basically no effect. When both NH3 and an amine were present, nucleation was more strongly enhanced than with just the amine present. Comparisons of nucleation rates to predictions and previous experimental work are discussed, and the sulfuric acid-base nucleation rates measured here are extrapolated to atmospheric conditions. The measurements suggest that atmospheric nucleation rates are significantly affected by synergistic interactions between ammonia and amines.

  5. Inactivation of invasive marine species in the process of conveying ballast water using OH based on a strong ionization discharge.

    PubMed

    Bai, Mindong; Zheng, Qilin; Tian, Yiping; Zhang, Zhitao; Chen, Cao; Cheng, Chao; Meng, Xiangying

    2016-06-01

    In this paper, invasive marine species in medium-salinity ballast water were inactivated using OH generated from a strong ionization discharge. The OH is determined by the concentration of oxygen active species combined with the effects of water jet cavitation. The results indicated that the OH concentration reached 7.62 μM, within 1 s, which is faster and higher than in conventional AOP methods. In a pilot-scale OH ballast water system with a capacity of 10 m(3)/h, algae were inactivated when CT value was 0.1 mg min/L with a contact time only 6 s. The viable and nonviable cells were determined using SYTOX Green nucleic acid stain and Flow cytometry. As a result, the OH treatment could be completed during the process of conveying the ballast water. In addition, the concentrations of relevant disinfection by-products (DBPs), such as trihalomethanes (THMs), haloacetic acids (HAAs), and bromate, were less than that required by the World Health Organization's drinking water standards, which suggest that the discharged ballast water posed no risks to the oceanic environment. Nevertheless, for conventional ozonation and electrolysis methods, the ballast water should be treated only in the treated tanks during the ship's voyage and form higher level DBPs.

  6. Inactivation of invasive marine species in the process of conveying ballast water using OH based on a strong ionization discharge.

    PubMed

    Bai, Mindong; Zheng, Qilin; Tian, Yiping; Zhang, Zhitao; Chen, Cao; Cheng, Chao; Meng, Xiangying

    2016-06-01

    In this paper, invasive marine species in medium-salinity ballast water were inactivated using OH generated from a strong ionization discharge. The OH is determined by the concentration of oxygen active species combined with the effects of water jet cavitation. The results indicated that the OH concentration reached 7.62 μM, within 1 s, which is faster and higher than in conventional AOP methods. In a pilot-scale OH ballast water system with a capacity of 10 m(3)/h, algae were inactivated when CT value was 0.1 mg min/L with a contact time only 6 s. The viable and nonviable cells were determined using SYTOX Green nucleic acid stain and Flow cytometry. As a result, the OH treatment could be completed during the process of conveying the ballast water. In addition, the concentrations of relevant disinfection by-products (DBPs), such as trihalomethanes (THMs), haloacetic acids (HAAs), and bromate, were less than that required by the World Health Organization's drinking water standards, which suggest that the discharged ballast water posed no risks to the oceanic environment. Nevertheless, for conventional ozonation and electrolysis methods, the ballast water should be treated only in the treated tanks during the ship's voyage and form higher level DBPs. PMID:27058879

  7. Micellar acid-base potentiometric titrations of weak acidic and/or insoluble drugs.

    PubMed

    Gerakis, A M; Koupparis, M A; Efstathiou, C E

    1993-01-01

    The effect of various surfactants [the cationics cetyl trimethyl ammonium bromide (CTAB) and cetyl pyridinium chloride (CPC), the anionic sodium dodecyl sulphate (SDS), and the nonionic polysorbate 80 (Tween 80)] on the solubility and ionization constant of some sparingly soluble weak acids of pharmaceutical interest was studied. Benzoic acid (and its 3-methyl-, 3-nitro-, and 4-tert-butyl-derivatives), acetylsalicylic acid, naproxen and iopanoic acid were chosen as model examples. Precise and accurate acid-base titrations in micellar systems were made feasible using a microcomputer-controlled titrator. The response curve, response time and potential drift of the glass electrode in the micellar systems were examined. The cationics CTAB and CPC were found to increase considerably the ionization constant of the weak acids (delta pKa ranged from -0.21 to -3.57), while the anionic SDS showed negligible effect and the nonionic Tween 80 generally decreased the ionization constants. The solubility of the acids in aqueous micellar and acidified micellar solutions was studied spectrophotometrically and it was found increased in all cases. Acetylsalicylic acid, naproxen, benzoic acid and iopanoic acid could be easily determined in raw material and some of them in pharmaceutical preparations by direct titration in CTAB-micellar system instead of using the traditional non-aqueous or back titrimetry. Precisions of 0.3-4.3% RSD and good correlation with the official tedious methods were obtained. The interference study of some excipients showed that a preliminary test should be carried out before the assay of formulations.

  8. Soil Studies: Applying Acid-Base Chemistry to Environmental Analysis.

    ERIC Educational Resources Information Center

    West, Donna M.; Sterling, Donna R.

    2001-01-01

    Laboratory activities for chemistry students focus attention on the use of acid-base chemistry to examine environmental conditions. After using standard laboratory procedures to analyze soil and rainwater samples, students use web-based resources to interpret their findings. Uses CBL probes and graphing calculators to gather and analyze data and…

  9. High School Students' Concepts of Acids and Bases.

    ERIC Educational Resources Information Center

    Ross, Bertram H. B.

    An investigation of Ontario high school students' understanding of acids and bases with quantitative and qualitative methods revealed misconceptions. A concept map, based on the objectives of the Chemistry Curriculum Guideline, generated multiple-choice items and interview questions. The multiple-choice test was administered to 34 grade 12…

  10. Statistical weighting of model-based optoacoustic reconstruction for minimizing artefacts caused by strong acoustic mismatch

    NASA Astrophysics Data System (ADS)

    Deán-Ben, X. Luís; Razansky, Daniel; Ntziachristos, Vasilis

    2011-03-01

    A modified quantitative inversion algorithm is presented that minimizes the effects of internal acoustic reflections or scattering in tomographic optoacoustic images. The inversion procedure in our model-based algorithm consists in solving a linear system of equations in which each individual equation corresponds to a given position of the acoustic transducer and to a given time instant. Thus, the modification that we propose in this work consists in weighting each equation of the linear system with the probability that the measured wave is not distorted by reflection or scattering phenomena. We show that the probability that a reflected or scattered wave is detected at a given position and at a given instant is approximately proportional to the size of the area in which the original wave could have been generated, which is dependent on the position of the transducer and on the time instant, so that such probability can be used to weight each equation of the linear system. Thereby, the contribution of the waves that propagate directly to the transducer to the reconstructed images is emphasized. We experimentally test the proposed inversion algorithm with tissue-mimicking agar phantoms in which air-gaps are included to cause reflections of the acoustic waves. The tomographic reconstructions obtained with the modification proposed herein show a clear reduction of the artefacts due to these acoustic phenomena with respect to the reconstructions yielded with the original algorithm. This performance is directly related to in-vivo small animal imaging applications involving imaging in the presence of bones, lungs, and other highly mismatched organs.

  11. A population-based analysis of clustering identifies a strong genetic contribution to lethal prostate cancer

    PubMed Central

    Nelson, Quentin; Agarwal, Neeraj; Stephenson, Robert; Cannon-Albright, Lisa A.

    2013-01-01

    Background: Prostate cancer is a common and often deadly cancer. Decades of study have yet to identify genes that explain much familial prostate cancer. Traditional linkage analysis of pedigrees has yielded results that are rarely validated. We hypothesize that there are rare segregating variants responsible for high-risk prostate cancer pedigrees, but recognize that within-pedigree heterogeneity is responsible for significant noise that overwhelms signal. Here we introduce a method to identify homogeneous subsets of prostate cancer, based on cancer characteristics, which show the best evidence for an inherited contribution. Methods: We have modified an existing method, the Genealogical Index of Familiality (GIF) used to show evidence for significant familial clustering. The modification allows a test for excess familial clustering of a subset of prostate cancer cases when compared to all prostate cancer cases. Results: Consideration of the familial clustering of eight clinical subsets of prostate cancer cases compared to the expected familial clustering of all prostate cancer cases identified three subsets of prostate cancer cases with evidence for familial clustering significantly in excess of expected. These subsets include prostate cancer cases diagnosed before age 50 years, prostate cancer cases with body mass index (BMI) greater than or equal to 30, and prostate cancer cases for whom prostate cancer contributed to death. Conclusions: This analysis identified several subsets of prostate cancer cases that cluster significantly more than expected when compared to all prostate cancer familial clustering. A focus on high-risk prostate cancer cases or pedigrees with these characteristics will reduce noise and could allow identification of the rare predisposition genes or variants responsible. PMID:23970893

  12. High night temperature strongly impacts TCA cycle, amino acid and polyamine biosynthetic pathways in rice in a sensitivity-dependent manner.

    PubMed

    Glaubitz, Ulrike; Erban, Alexander; Kopka, Joachim; Hincha, Dirk K; Zuther, Ellen

    2015-10-01

    Global climate change combined with asymmetric warming can have detrimental effects on the yield of crop plants such as rice (Oryza sativa L.). Little is known about metabolic responses of rice to high night temperature (HNT) conditions. Twelve cultivars with different HNT sensitivity were used to investigate metabolic changes in the vegetative stage under HNT compared to control conditions. Central metabolism, especially TCA cycle and amino acid biosynthesis, were strongly affected particularly in sensitive cultivars. Levels of several metabolites were correlated with HNT sensitivity. Furthermore, pool sizes of some metabolites negatively correlated with HNT sensitivity under control conditions, indicating metabolic pre-adaptation in tolerant cultivars. The polyamines putrescine, spermidine and spermine showed increased abundance in sensitive cultivars under HNT conditions. Correlations between the content of polyamines and 75 other metabolites indicated metabolic shifts from correlations with sugar-phosphates and 1-kestose under control to correlations with sugars and amino and organic acids under HNT conditions. Increased expression levels of ADC2 and ODC1, genes encoding enzymes catalysing the first committed steps of putrescine biosynthesis, were restricted to sensitive cultivars under HNT. Additionally, transcript levels of eight polyamine biosynthesis genes were correlated with HNT sensitivity. Responses to HNT in the vegetative stage result in distinct differences between differently responding cultivars with a dysregulation of central metabolism and an increase of polyamine biosynthesis restricted to sensitive cultivars under HNT conditions and a pre-adaptation of tolerant cultivars already under control conditions with higher levels of potentially protective compatible solutes. PMID:26208642

  13. High night temperature strongly impacts TCA cycle, amino acid and polyamine biosynthetic pathways in rice in a sensitivity-dependent manner.

    PubMed

    Glaubitz, Ulrike; Erban, Alexander; Kopka, Joachim; Hincha, Dirk K; Zuther, Ellen

    2015-10-01

    Global climate change combined with asymmetric warming can have detrimental effects on the yield of crop plants such as rice (Oryza sativa L.). Little is known about metabolic responses of rice to high night temperature (HNT) conditions. Twelve cultivars with different HNT sensitivity were used to investigate metabolic changes in the vegetative stage under HNT compared to control conditions. Central metabolism, especially TCA cycle and amino acid biosynthesis, were strongly affected particularly in sensitive cultivars. Levels of several metabolites were correlated with HNT sensitivity. Furthermore, pool sizes of some metabolites negatively correlated with HNT sensitivity under control conditions, indicating metabolic pre-adaptation in tolerant cultivars. The polyamines putrescine, spermidine and spermine showed increased abundance in sensitive cultivars under HNT conditions. Correlations between the content of polyamines and 75 other metabolites indicated metabolic shifts from correlations with sugar-phosphates and 1-kestose under control to correlations with sugars and amino and organic acids under HNT conditions. Increased expression levels of ADC2 and ODC1, genes encoding enzymes catalysing the first committed steps of putrescine biosynthesis, were restricted to sensitive cultivars under HNT. Additionally, transcript levels of eight polyamine biosynthesis genes were correlated with HNT sensitivity. Responses to HNT in the vegetative stage result in distinct differences between differently responding cultivars with a dysregulation of central metabolism and an increase of polyamine biosynthesis restricted to sensitive cultivars under HNT conditions and a pre-adaptation of tolerant cultivars already under control conditions with higher levels of potentially protective compatible solutes.

  14. Ligand- and Brønsted acid/base-switchable reaction pathways in gold(I)-catalyzed cycloisomerizations of allenoic acids.

    PubMed

    Handa, Sachin; Subramanium, Sri S; Ruch, Aaron A; Tanski, Joseph M; Slaughter, LeGrande M

    2015-04-01

    Gold-promoted cyclizations of 2,2-diaryl substituted γ-allenoic acids were found to give three isomeric lactone products, each of which could be obtained selectively by exploiting Brønsted acid/base and ligand effects. Simple 5-exo-trig cyclization products were favored by strong donor ligands or base additives, whereas weak donor ligands and a Brønsted acid additive gave isomeric enelactones resulting from double bond migration. Further optimization afforded a class of medicinally relevant bridged tricyclic lactones via a tandem hydroacyloxylation/hydroarylation process. Kinetic studies and control experiments indicated that the initial 5-exo-trig cyclization product serves as a branch point for further isomerization to the other lactone products via cooperative gold(I)/Brønsted acid catalysis.

  15. Activated human PMN synthesize and release a strongly fucosylated glycoform of alpha1-acid glycoprotein, which is transiently deposited in human myocardial infarction.

    PubMed

    Poland, Dennis C W; García Vallejo, Juan-Jesús; Niessen, Hans W M; Nijmeyer, Remco; Calafat, Jero; Hack, C Erik; Van het Hof, Bert; Van Dijk, Willem

    2005-08-01

    Alpha1-acid glycoprotein (AGP) is a major acute-phase protein present in human plasma as well as in polymorphonuclear leukocytes (PMN). In this report, we show that PMN synthesize a specific glycoform of AGP, which is stored in the specific and azurophilic granules. Activation of PMN results in the rapid release of soluble AGP. PMN AGP exhibits a substantially higher apparent molecular weight than plasma AGP (50-60 kD vs. 40-43 kD), owing to the presence of strongly fucosylated and sialylated polylactosamine units on its five N-linked glycans. PMN AGP is also released in vivo from activated PMN, as appeared from studies using well-characterized myocard slices of patients that had died within 2 weeks after an acute myocardial infarction. AGP was found deposited transiently on damaged cardiomyocytes in areas with infiltrating PMN only. It is interesting that this was inversely related to the deposition of activated complement C3. Strongly fucosylated and sialylated AGP glycoforms have the ability to bind to E-selectin and to inhibit complement activation. We suggest that AGP glycoforms in PMN provide an endogenous feedback-inhibitory response to excessive inflammation.

  16. When Military Parents Come Home: Building "Strong Families Strong Forces," a Home-Based Intervention for Military Families with Very Young Children

    ERIC Educational Resources Information Center

    Paris, Ruth; Acker, Michelle L.; Ross, Abigail M.; DeVoe, Ellen R.

    2011-01-01

    The long wars in Afghanistan and Iraq have presented unique challenges to military-connected families with very young children, yet few evidence-based services are available to support these families through deployment and reintegration. Although many military families have shown remarkable resilience throughout the intense demands of the wars,…

  17. The glmS ribozyme cofactor is a general acid-base catalyst.

    PubMed

    Viladoms, Júlia; Fedor, Martha J

    2012-11-21

    The glmS ribozyme is the first natural self-cleaving ribozyme known to require a cofactor. The d-glucosamine-6-phosphate (GlcN6P) cofactor has been proposed to serve as a general acid, but its role in the catalytic mechanism has not been established conclusively. We surveyed GlcN6P-like molecules for their ability to support self-cleavage of the glmS ribozyme and found a strong correlation between the pH dependence of the cleavage reaction and the intrinsic acidity of the cofactors. For cofactors with low binding affinities, the contribution to rate enhancement was proportional to their intrinsic acidity. This linear free-energy relationship between cofactor efficiency and acid dissociation constants is consistent with a mechanism in which the cofactors participate directly in the reaction as general acid-base catalysts. A high value for the Brønsted coefficient (β ~ 0.7) indicates that a significant amount of proton transfer has already occurred in the transition state. The glmS ribozyme is the first self-cleaving RNA to use an exogenous acid-base catalyst.

  18. The glmS Ribozyme Cofactor is a General Acid-Base Catalyst

    PubMed Central

    Viladoms, Julia; Fedor, Martha J.

    2012-01-01

    The glmS ribozyme is the first natural self-cleaving ribozyme known to require a cofactor. The D-glucosamine-6-phosphate (GlcN6P) cofactor has been proposed to serve as a general acid, but its role in the catalytic mechanism has not been established conclusively. We surveyed GlcN6P-like molecules for their ability to support self-cleavage of the glmS ribozyme and found a strong correlation between the pH dependence of the cleavage reaction and the intrinsic acidity of the cofactors. For cofactors with low binding affinities the contribution to rate enhancement was proportional to their intrinsic acidity. This linear free-energy relationship between cofactor efficiency and acid dissociation constants is consistent with a mechanism in which the cofactors participate directly in the reaction as general acid-base catalysts. A high value for the Brønsted coefficient (β ~ 0.7) indicates that a significant amount of proton transfer has already occurred in the transition state. The glmS ribozyme is the first self-cleaving RNA to use an exogenous acid-base catalyst. PMID:23113700

  19. A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model.

    PubMed

    Maurer, Patrick; Thomas, Vibin; Rivard, Ugo; Iftimie, Radu

    2010-07-28

    Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Bronsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa congruent with 1) as a model for excited-state HPTS( *) (pKa congruent with 1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

  20. A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model

    NASA Astrophysics Data System (ADS)

    Maurer, Patrick; Thomas, Vibin; Rivard, Ugo; Iftimie, Radu

    2010-07-01

    Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Brønsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa≅1) as a model for excited-state HPTS∗ (pKa≅1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

  1. Deoxyribonucleic acid base compositions of dermatophytes.

    PubMed

    Davison, F D; Mackenzie, D W; Owen, R J

    1980-06-01

    DNA was extracted and purified from 55 dermatophyte isolates representing 34 species of Trichophyton, Microsporum and Epidermophyton. The base compositions of the chromosomal DNA were determined by CsCl density gradient centrifugation and were found to be in the narrow range of 48.7 to 50.3 mol % G + C. A satellite DNA component assumed to be of mitochondrial origin was present in most strains, with a G + C content ranging from 14.7 to 30.8 mol % G + C. Heterogeneity in microscopic and colonial characteristics was not reflected in differences in the mean G + C content of the chromosomal DNAs. Strains varied in the G + C contents of satelite DNA, but these did not correlate with traditional species concepts.

  2. Use of Synergistic Interactions to Fabricate Strong, Tough, and Conductive Artificial Nacre Based on Graphene Oxide and Chitosan.

    PubMed

    Wan, Sijie; Peng, Jingsong; Li, Yuchen; Hu, Han; Jiang, Lei; Cheng, Qunfeng

    2015-10-27

    Graphene is the strongest and stiffest material, leading to the development of promising applications in many fields. However, the assembly of graphene nanosheets into macrosized nanocomposites for practical applications remains a challenge. Nacre in its natural form sets the "gold standard" for toughness and strength, which serves as a guide to the assembly of graphene nanosheets into high-performance nanocomposites. Here we show the strong, tough, conductive artificial nacre based on graphene oxide through synergistic interactions of hydrogen and covalent bonding. Tensile strength and toughness was 4 and 10 times higher, respectively, than that of natural nacre. The exceptional integrated strong and tough artificial nacre has promising applications in aerospace, artificial muscle, and tissue engineering, especially for flexible supercapacitor electrodes due to its high electrical conductivity. The use of synergistic interactions is a strategy for the development of high-performance nanocomposites. PMID:26352293

  3. Determination of acid-base dissociation constants of very weak zwitterionic heterocyclic bases by capillary zone electrophoresis.

    PubMed

    Ehala, Sille; Grishina, Anastasiya A; Sheshenev, Andrey E; Lyapkalo, Ilya M; Kašička, Václav

    2010-12-17

    Thermodynamic acid-base dissociation (ionization) constants (pK(a)) of seven zwitterionic heterocyclic bases, first representatives of new heterocyclic family (2,3,5,7,8,9-hexahydro-1H-diimidazo[1,2-c:2',1'-f][1,3,2]diazaphosphinin-4-ium-5-olate 5-oxides), originally designed as chiral Lewis base catalysts for enantioselective reactions, were determined by capillary zone electrophoresis (CZE). The pK(a) values of the above very weak zwitterionic bases were determined from the dependence of their effective electrophoretic mobility on pH in strongly acidic background electrolytes (pH 0.85-2.80). Prior to pK(a) calculation by non-linear regression analysis, the CZE measured effective mobilities were corrected to reference temperature, 25°C, and constant ionic strength, 25 mM. Thermodynamic pK(a) values of the analyzed zwitterionic heterocyclic bases were found to be particularly low, in the range 0.04-0.32. Moreover, from the pH dependence of effective mobility of the bases, some other relevant characteristics, such as actual and absolute ionic mobilities and hydrodynamic radii of the acidic cationic forms of the bases were determined.

  4. Relativistic effects on acidities and basicities of Brønsted acids and bases containing gold.

    PubMed

    Koppel, Ilmar A; Burk, Peeter; Kasemets, Kalev; Koppel, Ivar

    2013-11-01

    It is usually believed that relativistic effects as described by the Dirac-Schrödinger equation (relative to the classical or time-independent Schrödinger equation) are of little importance in chemistry. A closer look, however, reveals that some important and widely known properties (e.g., gold is yellow, mercury is liquid at room temperature) stem from relativistic effects. So far the influence of relativistic effects on the acid-base properties has been mostly ignored. Here we show that at least for compounds of gold such omission is completely erroneous and would lead to too high basicity and too low acidity values with errors in the range of 25-55 kcal mol(-1) (or 20 to 44 powers of ten in pK(a) units) in the gas-phase. These findings have important implications for the design of new superstrong acids and bases, and for the understanding of gold-catalysed reactions.

  5. Strong electroactive biodegradable shape memory polymer networks based on star-shaped polylactide and aniline trimer for bone tissue engineering.

    PubMed

    Xie, Meihua; Wang, Ling; Ge, Juan; Guo, Baolin; Ma, Peter X

    2015-04-01

    Preparation of functional shape memory polymer (SMP) for tissue engineering remains a challenge. Here the synthesis of strong electroactive shape memory polymer (ESMP) networks based on star-shaped polylactide (PLA) and aniline trimer (AT) is reported. Six-armed PLAs with various chain lengths were chemically cross-linked to synthesize SMP. After addition of an electroactive AT segment into the SMP, ESMP was obtained. The polymers were characterized by (1)H NMR, GPC, FT-IR, CV, DSC, DMA, tensile test, and degradation test. The SMP and ESMP exhibited strong mechanical properties (modulus higher than GPa) and excellent shape memory performance: short recovery time (several seconds), high recovery ratio (over 94%), and high fixity ratio (almost 100%). Moreover, cyclic voltammetry test confirmed the electroactivity of the ESMP. The ESMP significantly enhanced the proliferation of C2C12 cells compared to SMP and linear PLA (control). In addition, the ESMP greatly improved the osteogenic differentiation of C2C12 myoblast cells compared to PH10 and PLA in terms of ALP enzyme activity, immunofluorescence staining, and relative gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). These intelligent SMPs and electroactive SMP with strong mechanical properties, tunable degradability, good electroactivity, biocompatibility, and enhanced osteogenic differentiation of C2C12 cells show great potential for bone regeneration.

  6. Nucleic acid-based nanoengineering: novel structures for biomedical applications

    PubMed Central

    Li, Hanying; LaBean, Thomas H.; Leong, Kam W.

    2011-01-01

    Nanoengineering exploits the interactions of materials at the nanometre scale to create functional nanostructures. It relies on the precise organization of nanomaterials to achieve unique functionality. There are no interactions more elegant than those governing nucleic acids via Watson–Crick base-pairing rules. The infinite combinations of DNA/RNA base pairs and their remarkable molecular recognition capability can give rise to interesting nanostructures that are only limited by our imagination. Over the past years, creative assembly of nucleic acids has fashioned a plethora of two-dimensional and three-dimensional nanostructures with precisely controlled size, shape and spatial functionalization. These nanostructures have been precisely patterned with molecules, proteins and gold nanoparticles for the observation of chemical reactions at the single molecule level, activation of enzymatic cascade and novel modality of photonic detection, respectively. Recently, they have also been engineered to encapsulate and release bioactive agents in a stimulus-responsive manner for therapeutic applications. The future of nucleic acid-based nanoengineering is bright and exciting. In this review, we will discuss the strategies to control the assembly of nucleic acids and highlight the recent efforts to build functional nucleic acid nanodevices for nanomedicine. PMID:23050076

  7. Use of a polystyrene-divinylbenzene-based weakly acidic cation-exchange resin column and propionic acid as an eluent in ion-exclusion/adsorption chromatography of aliphatic carboxylic acids and ethanol in food samples.

    PubMed

    Mori, Masanobu; Hironaga, Takahiro; Kajiwara, Hiroe; Nakatani, Nobutake; Kozaki, Daisuke; Itabashi, Hideyuki; Tanaka, Kazuhiko

    2011-01-01

    We developed an ion-exclusion/adsorption chromatography (IEAC) method employing a polystyrene-divinylbenzene-based weakly acidic cation-exchange resin (PS-WCX) column with propionic acid as the eluent for the simultaneous determination of multivalent aliphatic carboxylic acids and ethanol in food samples. The PS-WCX column well resolved mono-, di-, and trivalent carboxylic acids in the acidic eluent. Propionic acid as the eluent gave a higher signal-to-noise ratio, and enabled sensitive conductimetric detection of analyte acids. We found the optimal separation condition to be the combination of a PS-WCX column and 20-mM propionic acid. Practical applicability of the developed method was confirmed by using a short precolumn with a strongly acidic cation-exchange resin in the H(+)-form connected before the separation column; this was to remove cations from food samples by converting them to hydrogen ions. Consequently, common carboxylic acids and ethanol in beer, wine, and soy sauce were successfully separated by the developed method.

  8. Preparation of LaF3:Eu3+ Based Inorganic-Organic Hybrid Nanostructures via an Ion Exchange Method and Their Strong Luminescence.

    PubMed

    Wang, Xiaojing; Yang, Yi; Chen, Nan; Liu, Bingfa; Liu, Guihua

    2016-04-01

    Lanthanide doped inorganic-organic hybrid nanostructures have received much attention in recent years due to their strong luminescence sensitized by organic ligands via an energy transfer route. In this work, an ion exchange method was used to prepare Eu3+ doped LaF3 based inorganic-organic hybrid nanostructures with organic ligands. The undoped LaF3 nanoparticles were first synthesized by a hydrothermal method, and Eu3+ ions were then ion exchanged into these LaF. nanoparticles to form the Eu3+ doped LaF3 nanoparticles, which were then used to prepare the inorganic-organic hybrid nanostructures with benzoic acid and 2-thenoyltrifluoroacetone. As a result of the luminescence sensitization, strong luminescence was observed in these inorganic-organic hybrid nanostructures, and the luminescence enhancement was over 40 times. Dependence of the luminescence of the hybrid nanostructures on the doping concentration and amount of organic ligands was studied in detail, and optimization was conducted to obtain the maximum luminescence for the hybrid nanostructures. PMID:27451698

  9. Acid-Base Interactions of Polystyrene Sulfonic Acid in Amorphous Solid Dispersions Using a Combined UV/FTIR/XPS/ssNMR Study.

    PubMed

    Song, Yang; Zemlyanov, Dmitry; Chen, Xin; Nie, Haichen; Su, Ziyang; Fang, Ke; Yang, Xinghao; Smith, Daniel; Byrn, Stephen; Lubach, Joseph W

    2016-02-01

    This study investigates the potential drug-excipient interactions of polystyrene sulfonic acid (PSSA) and two weakly basic anticancer drugs, lapatinib (LB) and gefitinib (GB), in amorphous solid dispersions. Based on the strong acidity of the sulfonic acid functional group, PSSA was hypothesized to exhibit specific intermolecular acid-base interactions with both model basic drugs. Ultraviolet (UV) spectroscopy identified red shifts, which correlated well with the color change observed in lapatinib-PSSA solutions. Fourier transform infrared (FTIR) spectra suggest the protonation of the quinazoline nitrogen atom in both model compounds, which agrees well with data from the crystalline ditosylate salt of lapatinib. X-ray photoelectron spectroscopy (XPS) detected increases in binding energy of the basic nitrogen atoms in both lapatinib and gefitinib, strongly indicating protonation of these nitrogen atoms. (15)N solid-state NMR spectroscopy provided direct spectroscopic evidence for protonation of the quinazoline nitrogen atoms in both LB and GB, as well as the secondary amine nitrogen atom in LB and the tertiary amine nitrogen atom in GB. The observed chemical shifts in the LB-PSSA (15)N spectrum also agree very well with the lapatinib ditosylate salt where proton transfer is known. Additionally, the dissolution and physical stability behaviors of both amorphous solid dispersions were examined. PSSA was found to significantly improve the dissolution of LB and GB and effectively inhibit the crystallization of LB and GB under accelerated storage conditions due to the beneficial strong intermolecular acid-base interaction between the sulfonic acid groups and basic nitrogen centers.

  10. Acid-Base Interactions of Polystyrene Sulfonic Acid in Amorphous Solid Dispersions Using a Combined UV/FTIR/XPS/ssNMR Study.

    PubMed

    Song, Yang; Zemlyanov, Dmitry; Chen, Xin; Nie, Haichen; Su, Ziyang; Fang, Ke; Yang, Xinghao; Smith, Daniel; Byrn, Stephen; Lubach, Joseph W

    2016-02-01

    This study investigates the potential drug-excipient interactions of polystyrene sulfonic acid (PSSA) and two weakly basic anticancer drugs, lapatinib (LB) and gefitinib (GB), in amorphous solid dispersions. Based on the strong acidity of the sulfonic acid functional group, PSSA was hypothesized to exhibit specific intermolecular acid-base interactions with both model basic drugs. Ultraviolet (UV) spectroscopy identified red shifts, which correlated well with the color change observed in lapatinib-PSSA solutions. Fourier transform infrared (FTIR) spectra suggest the protonation of the quinazoline nitrogen atom in both model compounds, which agrees well with data from the crystalline ditosylate salt of lapatinib. X-ray photoelectron spectroscopy (XPS) detected increases in binding energy of the basic nitrogen atoms in both lapatinib and gefitinib, strongly indicating protonation of these nitrogen atoms. (15)N solid-state NMR spectroscopy provided direct spectroscopic evidence for protonation of the quinazoline nitrogen atoms in both LB and GB, as well as the secondary amine nitrogen atom in LB and the tertiary amine nitrogen atom in GB. The observed chemical shifts in the LB-PSSA (15)N spectrum also agree very well with the lapatinib ditosylate salt where proton transfer is known. Additionally, the dissolution and physical stability behaviors of both amorphous solid dispersions were examined. PSSA was found to significantly improve the dissolution of LB and GB and effectively inhibit the crystallization of LB and GB under accelerated storage conditions due to the beneficial strong intermolecular acid-base interaction between the sulfonic acid groups and basic nitrogen centers. PMID:26716395

  11. α-Ketoglutarate regulates acid-base balance through an intrarenal paracrine mechanism

    PubMed Central

    Tokonami, Natsuko; Morla, Luciana; Centeno, Gabriel; Mordasini, David; Ramakrishnan, Suresh Krishna; Nikolaeva, Svetlana; Wagner, Carsten A.; Bonny, Olivier; Houillier, Pascal; Doucet, Alain; Firsov, Dmitri

    2013-01-01

    Paracrine communication between different parts of the renal tubule is increasingly recognized as an important determinant of renal function. Previous studies have shown that changes in dietary acid-base load can reverse the direction of apical α-ketoglutarate (αKG) transport in the proximal tubule and Henle’s loop from reabsorption (acid load) to secretion (base load). Here we show that the resulting changes in the luminal concentrations of αKG are sensed by the αKG receptor OXGR1 expressed in the type B and non-A–non-B intercalated cells of the connecting tubule (CNT) and the cortical collecting duct (CCD). The addition of 1 mM αKG to the tubular lumen strongly stimulated Cl–-dependent HCO3– secretion and electroneutral transepithelial NaCl reabsorption in microperfused CCDs of wild-type mice but not Oxgr1–/– mice. Analysis of alkali-loaded mice revealed a significantly reduced ability of Oxgr1–/– mice to maintain acid-base balance. Collectively, these results demonstrate that OXGR1 is involved in the adaptive regulation of HCO3– secretion and NaCl reabsorption in the CNT/CCD under acid-base stress and establish αKG as a paracrine mediator involved in the functional coordination of the proximal and the distal parts of the renal tubule. PMID:23934124

  12. Acid-base metabolism: implications for kidney stones formation.

    PubMed

    Hess, Bernhard

    2006-04-01

    The physiology and pathophysiology of renal H+ ion excretion and urinary buffer systems are reviewed. The main focus is on the two major conditions related to acid-base metabolism that cause kidney stone formation, i.e., distal renal tubular acidosis (dRTA) and abnormally low urine pH with subsequent uric acid stone formation. Both the entities can be seen on the background of disturbances of the major urinary buffer system, NH3+ <--> NH4+. On the one hand, reduced distal tubular secretion of H+ ions results in an abnormally high urinary pH and either incomplete or complete dRTA. On the other hand, reduced production/availability of NH4+ is the cause of an abnormally low urinary pH, which predisposes to uric acid stone formation. Most recent research indicates that the latter abnormality may be a renal manifestation of the increasingly prevalent metabolic syndrome. Despite opposite deviations from normal urinary pH values, both the dRTA and uric acid stone formation due to low urinary pH require the same treatment, i.e., alkali. In the dRTA, alkali is needed for improving the body's buffer capacity, whereas the goal of alkali treatment in uric acid stone formers is to increase the urinary pH to 6.2-6.8 in order to minimize uric acid crystallization.

  13. Acid/base account and minesoils: A review

    SciTech Connect

    Hossner, L.R.; Brandt, J.E.

    1997-12-31

    Generation of acidity from the oxidation of iron sulfides (FeS{sub 2}) is a common feature of geological materials exposed to the atmosphere by mining activities. Acid/base accounting (ABA) has been the primary method to evaluate the acid- or alkaline-potential of geological materials and to predict if weathering of these materials will have an adverse effect on terrestrial and aquatic environments. The ABA procedure has also been used to evaluate minesoils at different stages of weathering and, in some cases, to estimate lime requirements. Conflicting assessments of the methodology have been reported in the literature. The ABA is the fastest and easiest way to evaluate the acid-forming characteristics of overburden materials; however, accurate evaluations sometimes require that ABA data be examined in conjunction with additional sample information and results from other analytical procedures. The end use of ABA data, whether it be for minesoil evaluation or water quality prediction, will dictate the method`s interpretive criteria. Reaction kinetics and stoichiometry may vary and are not clearly defined for all situations. There is an increasing awareness of the potential for interfering compounds, particularly siderite (FeCO{sub 3}), to be present in geological materials associated with coal mines. Hardrock mines, with possible mixed sulfide mineralogy, offer a challenge to the ABA, since acid generation may be caused by minerals other than pyrite. A combination of methods, static and kinetic, is appropriate to properly evaluate the presence of acid-forming materials.

  14. Students' Understanding of Acids/Bases in Organic Chemistry Contexts

    ERIC Educational Resources Information Center

    Cartrette, David P.; Mayo, Provi M.

    2011-01-01

    Understanding key foundational principles is vital to learning chemistry across different contexts. One such foundational principle is the acid/base behavior of molecules. In the general chemistry sequence, the Bronsted-Lowry theory is stressed, because it lends itself well to studying equilibrium and kinetics. However, the Lewis theory of…

  15. Turkish Prospective Chemistry Teachers' Alternative Conceptions about Acids and Bases

    ERIC Educational Resources Information Center

    Boz, Yezdan

    2009-01-01

    The purpose of this study was to obtain prospective chemistry teachers' conceptions about acids and bases concepts. Thirty-eight prospective chemistry teachers were the participants. Data were collected by means of an open-ended questionnaire and semi-structured interviews. Analysis of data indicated that most prospective teachers did not have…

  16. Thymine, adenine and lipoamino acid based gene delivery systems.

    PubMed

    Skwarczynski, Mariusz; Ziora, Zyta M; Coles, Daniel J; Lin, I-Chun; Toth, Istvan

    2010-05-14

    A novel class of thymine, adenine and lipoamino acid based non-viral carriers for gene delivery has been developed. Their ability to bind to DNA by hydrogen bonding was confirmed by NMR diffusion, isothermal titration calorimetry and transmission electron microscopy experiments.

  17. Photoresponsive self-assemblies based on fatty acids.

    PubMed

    Fameau, A-L; Arnould, A; Lehmann, M; von Klitzing, R

    2015-02-18

    Photoresponsive surfactant system based on fatty acids has been developed by the introduction in aqueous solution of a photoacid generator (PAG). Self-assembly transitions are triggered by UV irradiation due to a pH change induced by the presence of PAG.

  18. Acid-Base Disorders--A Computer Simulation.

    ERIC Educational Resources Information Center

    Maude, David L.

    1985-01-01

    Describes and lists a program for Apple Pascal Version 1.1 which investigates the behavior of the bicarbonate-carbon dioxide buffer system in acid-base disorders. Designed specifically for the preclinical medical student, the program has proven easy to use and enables students to use blood gas parameters to arrive at diagnoses. (DH)

  19. A Schiff base formed from sulfanilic acid and dimethylformamide.

    PubMed

    Hempel, A; Camerman, N; Mastropaolo, D; Camerman, A

    1999-04-15

    The crystal structure the Schiff base contains one 4-dimethylaminomethyleneaminobenzenesulfonic acid molecule in zwitterionic form [4-(dimethylaminomethyleneammonio)benzenesulfonate], and one water molecule in the asymmetric unit (C9H12N2O3S.H2O). Protonation occurs at nitrogen atom N1, but the charge is delocalized.

  20. Using Spreadsheets to Produce Acid-Base Titration Curves.

    ERIC Educational Resources Information Center

    Cawley, Martin James; Parkinson, John

    1995-01-01

    Describes two spreadsheets for producing acid-base titration curves, one uses relatively simple cell formulae that can be written into the spreadsheet by inexperienced students and the second uses more complex formulae that are best written by the teacher. (JRH)

  1. Silica-Based, Hyper-Crosslinked Acid Stable Stationary Phases for High Performance Liquid Chromatography

    PubMed Central

    Zhang, Yu; Luo, Hao; Carr, Peter W.

    2011-01-01

    A new family of Hyper-Crosslinked (HC) phases has been recently introduced for use under very aggressive acid conditions including those encountered in ultra-fast, high temperature Two-Dimensional Liquid Chromatography (2DLC). This type of stationary phase showed significantly enhanced acid and thermal stability compared to the most acid stable, commercial RPLC phases. In addition, the use of “orthogonal” chemistry to make surface-confined polymer networks ensures good reproducibility and high efficiency. One of the most interesting features of the HC phases is the ability to derivatize the surface aromatic groups with various functional groups. This led to the development of a family of hyper-crosslinked phases possessing a wide variety of chromatographic selectivities by attaching hydrophobic (e.g. –C8), ionizable (e.g. -COOH, -SO3H), aromatic (e.g. –toluene) or polar (e.g. -OH) species to the aromatic polymer network. HC reversed phases with various degrees of hydrophobicity and mixed-mode HC phases with added strong and weak cation exchange sites have been synthesized, characterized and applied. These silica-based acid-stable HC phases, with their attractive chromatographic properties, should be very useful in the separations of bases or biological analytes in acidic media, especially at elevated temperatures. This work reviews the prior research on HC phases and introduces a novel HC phase made by alternative chemistry. PMID:21906745

  2. Staying Strong With Schools: A Civilian School-Based Intervention to Promote Resilience for Military-Connected Children.

    PubMed

    Ohye, Bonnie; Kelly, Hope; Chen, Yang; Zakarian, Rebecca J; Simon, Naomi M; Bui, Eric

    2016-08-01

    Since September 11, 2001, over 2 million U.S. service members have been deployed to Iraq or Afghanistan, resulting in hundreds of thousands of military-connected children (MCC) having experienced a parental deployment. Although parental deployments have significantly burdened these children, few evidence-based interventions designed to support their resilience to these stressors are available. To address this gap, we developed a civilian school-based intervention to promote resilience in MCC living in the community. Our intervention, Staying Strong With Schools (SSWS), aims to deliver: a training to all school professionals early in the school year to educate them about challenges for children and families experiencing parental deployment and signs of deployment-related distress; and a year-long training for the school guidance counselor who coordinates communication and provides psychosocial support to MCC within the school community. We piloted SSWS in two civilian elementary schools and found promising feasibility and acceptability. PMID:27483526

  3. Mechanisms of Acid and Base Secretion by the Airway Epithelium

    PubMed Central

    Fischer, Horst; Widdicombe, Jonathan H.

    2010-01-01

    SUMMARY One of the main functions of the airway epithelium is to inactivate and remove infectious particles from inhaled air and thereby prevent infection of the distal lung. This function is achieved by mucociliary and cough clearance and by antimicrobial factors present in the airway surface liquid (ASL). There are indications that airway defenses are affected by the pH of the ASL and historically, acidification of the airway surfaces has been suggested as a measure of airway disease. However, even in health, the ASL is slightly acidic, and this acidity might be part of normal airway defense. Only recently research has focused on the mechanisms responsible for acid and base secretion into the ASL. Advances resulted from research into the airway disease associated with cystic fibrosis (CF) after it was found that the CFTR C1- channel conducts HCO3- and, therefore, may contribute to ASL pH. However, the acidity of the ASL indicated parallel mechanisms for H+ secretion. Recent investigations identified several H+ transporters in the apical membrane of the airway epithelium. These include H+ channels and ATP-driven H+ pumps, including a non-gastric isoform of the H+-K+ ATPase and a vacuolar-type H+ ATPase. Current knowledge of acid and base transporters and their potential roles in airway mucosal pH regulation is reviewed here. PMID:17091214

  4. Structure-Based Design of Potent Bcl-2/Bcl-xL Inhibitors with Strong in Vivo Antitumor Activity

    SciTech Connect

    Zhou, Haibin; Aguilar, Angelo; Chen, Jianfang; Bai, Longchuan; Liu, Liu; Meagher, Jennifer L.; Yang, Chao-Yie; McEachern, Donna; Cong, Xin; Stuckey, Jeanne A.; Wang, Shaomeng

    2012-08-21

    Bcl-2 and Bcl-xL are key apoptosis regulators and attractive cancer therapeutic targets. We have designed and optimized a class of small-molecule inhibitors of Bcl-2 and Bcl-xL containing a 4,5-diphenyl-1H-pyrrole-3-carboxylic acid core structure. A 1.4 {angstrom} resolution crystal structure of a lead compound, 12, complexed with Bcl-xL has provided a basis for our optimization. The most potent compounds, 14 and 15, bind to Bcl-2 and Bcl-xL with subnanomolar K{sub i} values and are potent antagonists of Bcl-2 and Bcl-xL in functional assays. Compounds 14 and 15 inhibit cell growth with low nanomolar IC{sub 50} values in multiple small-cell lung cancer cell lines and induce robust apoptosis in cancer cells at concentrations as low as 10 nM. Compound 14 also achieves strong antitumor activity in an animal model of human cancer.

  5. Primordial transport of sugars and amino acids via Schiff bases

    NASA Astrophysics Data System (ADS)

    Stillwell, William; Rau, Aruna

    1981-09-01

    Experimental support is given for a model concerning the origin of a primordial transport system. The model is based on the facilitated diffusion of amino acids stimulated by aliphatic aldehyde carriers and sugars stimulated by aliphatic amine carriers. The lipid-soluble diffusing species is the Schiff base. The possible role of this simple transport system in the origin of an early protocell is discussed.

  6. Strong Acid Mixture and Sequential Geochemical Arsenic Extractions in Surface Sediments from the Santa Maria La Reforma Coastal Lagoon, Mexico: A Bioavailability Assessment.

    PubMed

    Rivera-Hernández, José R; Green-Ruiz, Carlos

    2016-02-01

    Thirty-three sediment samples were collected from the Santa Maria La Reforma coastal lagoon and digested by way of a strong acid mixture and sequential arsenic (As)-extraction method to determine the arsenic (As) content and bioavailability. The As content was determined by atomic fluorescence spectrometry. In addition, grain-size analyses were performed, and organic carbon, carbonate, and iron (Fe) and manganese (Mn) concentrations were determined. Fe and Mn determination was performed by atomic absorption spectroscopy. A Pearson correlation matrix and As enrichment factors were calculated. Sediment concentrations from Santa Maria La Reforma ranged from 3.6 to 25 µg As g(-1) with an average of 13.4 ± 7.6 µg As g(-1). The highest values were observed in the northern (Playa Colorada), north-central (Mocorito River discharge zone), and southern zones ("El Tule" agricultural drain). Most samples were classified as exhibiting no or minor As enrichment and were lower than the threshold effect level (TEL; 7.24 µg g(-1)) for biota (MacDonald et al. in Ecotoxicology 5:253-278, 1996). Low bioavailable As values (<3 %) were measured in the majority of the sediment. The highest As percentages were associated with the oxyhydroxide fraction (F5). The results indicate that As bioavailability is negligible. PMID:26743199

  7. Interleukin-22 binding protein (IL-22BP) is constitutively expressed by a subset of conventional dendritic cells and is strongly induced by retinoic acid

    PubMed Central

    Martin, JCJ; Bériou, G; Heslan, M; Chauvin, C; Utriainen, L; Aumeunier, A; Scott, CL; Mowat, A; Cerovic, V; Houston, SA; Leboeuf, M; Hubert, FX; Hémont, C; Merad, M; Milling, S; Josien, R

    2014-01-01

    IL-22 is mainly produced at barrier surfaces by T cells and innate lymphoid cells and is crucial to maintain epithelial integrity. However, dysregulated IL-22 action leads to deleterious inflammation and is involved in diseases such as psoriasis, intestinal inflammation and cancer. IL-22BP is a soluble inhibitory IL-22 receptor and may represent a crucial regulator of IL-22. We show both in rats and mice that, in the steady state, the main source of IL-22BP is constituted by a subset of conventional dendritic cells (DC) in lymphoid and non lymphoid tissues. In mouse intestine, IL-22BP was specifically expressed in lamina propria CD103+CD11b+ DC. In humans, IL-22BP was expressed in immature monocyte-derived DC (MDDC) and strongly induced by retinoic acid (RA) but dramatically reduced upon maturation. Our data suggest that a subset of immature DC may actively participate in the regulation of IL-22 activity in the gut by producing high levels of IL-22BP. PMID:23653115

  8. Unprecedented access to strong and ductile poly(lactic acid) by introducing In Situ Nanofibrillar Poly(butylene succinate) for green packaging.

    PubMed

    Xie, Lan; Xu, Huan; Niu, Ben; Ji, Xu; Chen, Jun; Li, Zhong-Ming; Hsiao, Benjamin S; Zhong, Gan-Ji

    2014-11-10

    The notion of toughening poly(lactic acid) (PLA) by adding flexible biopolymers has generated enormous interest but has yielded few desirable advances, mainly blocked by the sacrifice of strength and stiffness due to uncontrollable phase morphology and poor interfacial interactions. Here the phase control methodology, that is, intense extrusion compounding followed by "slit die extrusion-hot stretching-quenching" technique, was proposed to construct well-aligned, stiff poly(butylene succinate) (PBS) nanofibrils in the PLA matrix for the first time. We show that generating nanosized discrete droplets of PBS phase during extrusion compounding is key to enable the development of in situ nanofibrillar PBS assisted by the shearing/stretching field. The size of PBS nanofibrils strongly dependent on the PBS content, showing an increased average diameter from 83 to 116 and 236 nm for the composites containing 10, 20, and 40 wt % nanofibrils, respectively. More importantly, hybrid shish-kebab superstructure anchoring ordered PLA kebabs were induced by the PBS nanofibrils serving as the central shish, conferring the creation of tenacious interfacial crystalline ligaments. The exceptional combination of strength, modulus, and ductility for the composites loaded 40 wt % PBS nanofibrils were demonstrated, outperforming pure PLA with the increments of 31, 51, and 72% in strength, modulus, and elongation at break (56.4 MPa, 1702 MPa, and 92.4%), respectively. The high strength, modulus, and ductility are unprecedented for PLA and are in great potential need for packaging applications.

  9. Strong Acid Mixture and Sequential Geochemical Arsenic Extractions in Surface Sediments from the Santa Maria La Reforma Coastal Lagoon, Mexico: A Bioavailability Assessment.

    PubMed

    Rivera-Hernández, José R; Green-Ruiz, Carlos

    2016-02-01

    Thirty-three sediment samples were collected from the Santa Maria La Reforma coastal lagoon and digested by way of a strong acid mixture and sequential arsenic (As)-extraction method to determine the arsenic (As) content and bioavailability. The As content was determined by atomic fluorescence spectrometry. In addition, grain-size analyses were performed, and organic carbon, carbonate, and iron (Fe) and manganese (Mn) concentrations were determined. Fe and Mn determination was performed by atomic absorption spectroscopy. A Pearson correlation matrix and As enrichment factors were calculated. Sediment concentrations from Santa Maria La Reforma ranged from 3.6 to 25 µg As g(-1) with an average of 13.4 ± 7.6 µg As g(-1). The highest values were observed in the northern (Playa Colorada), north-central (Mocorito River discharge zone), and southern zones ("El Tule" agricultural drain). Most samples were classified as exhibiting no or minor As enrichment and were lower than the threshold effect level (TEL; 7.24 µg g(-1)) for biota (MacDonald et al. in Ecotoxicology 5:253-278, 1996). Low bioavailable As values (<3 %) were measured in the majority of the sediment. The highest As percentages were associated with the oxyhydroxide fraction (F5). The results indicate that As bioavailability is negligible.

  10. Exploring a new SPION-based MRI contrast agent with excellent water-dispersibility, high specificity to cancer cells and strong MR imaging efficacy.

    PubMed

    Ma, Xuehua; Gong, An; Chen, Bin; Zheng, Jianjun; Chen, Tianxiang; Shen, Zheyu; Wu, Aiguo

    2015-02-01

    Advances in contrast agents have greatly enhanced the sensitivity of magnetic resonance imaging (MRI) technique for early diagnosis of cancer. However, the commercial superparamagnetic iron oxide nanoparticles (SPION)-based contrast agents synthesized by co-precipitation method are not monodisperse with irregular morphologies and ununiform sizes. Other reported SPION-based contrast agents synthesized by solvothermal method or thermal decomposition method are limited by the bad water-dispersibility and low specificity to cancer cells. Herein, we propose a new strategy for exploring SPION-based MRI contrast agents with excellent water-dispersibility and high specificity to cancer cells. The SPION was synthesized by a polyol method and then entrapped into albumin nanospheres (AN). After that, a ligand folic acid (FA) was conjugated onto the surface of the AN to construct a SPION-AN-FA composite. The transmission electron microscope (TEM) and dynamic light scattering (DLS) results indicate that the SPION-AN-FA has a spherical shape, a uniform size and an excellent water-dispersibility (polydispersity index (PDI) <0.05). The results of laser scanning confocal microscope (LSCM) and flow cytometry demonstrate that the SPION-AN-FA nanoparticles are highly specific to MCF-7 and SPC-A-1 cells due to the recognition of ligand FA and folate receptor α (FRα). The r2/r1 value of SPION-AN-FA is around 40, which is much higher than that of Resovist(®) indicating that our SPION-AN-FA has a stronger T2 shortening effect. The T2-weighted images of MCF-7 cells incubated with SPION-AN-FA are significantly darker than those of MCF-7 cells incubated with AN, indicating that our SPION-AN-FA has a strong MR imaging efficacy. In view of the excellent water-dispersibility, the high specificity to cancer cells and the strong MR imaging efficacy, our SPION-AN-FA can be used as a negative MR contrast agent.

  11. Model for acid-base chemistry in nanoparticle growth (MABNAG)

    NASA Astrophysics Data System (ADS)

    Yli-Juuti, T.; Barsanti, K.; Hildebrandt Ruiz, L.; Kieloaho, A.-J.; Makkonen, U.; Petäjä, T.; Ruuskanen, T.; Kulmala, M.; Riipinen, I.

    2013-03-01

    Climatic effects of newly-formed atmospheric secondary aerosol particles are to a large extent determined by their condensational growth rates. However, all the vapors condensing on atmospheric nanoparticles and growing them to climatically relevant sizes are not identified yet and the effects of particle phase processes on particle growth rates are poorly known. Besides sulfuric acid, organic compounds are known to contribute significantly to atmospheric nanoparticle growth. In this study a particle growth model MABNAG (Model for Acid-Base chemistry in NAnoparticle Growth) was developed to study the effect of salt formation on nanoparticle growth, which has been proposed as a potential mechanism lowering the equilibrium vapor pressures of organic compounds through dissociation in the particle phase and thus preventing their evaporation. MABNAG is a model for monodisperse aqueous particles and it couples dynamics of condensation to particle phase chemistry. Non-zero equilibrium vapor pressures, with both size and composition dependence, are considered for condensation. The model was applied for atmospherically relevant systems with sulfuric acid, one organic acid, ammonia, one amine and water in the gas phase allowed to condense on 3-20 nm particles. The effect of dissociation of the organic acid was found to be small under ambient conditions typical for a boreal forest site, but considerable for base-rich environments (gas phase concentrations of about 1010 cm-3 for the sum of the bases). The contribution of the bases to particle mass decreased as particle size increased, except at very high gas phase concentrations of the bases. The relative importance of amine versus ammonia did not change significantly as a function of particle size. While our results give a reasonable first estimate on the maximum contribution of salt formation to nanoparticle growth, further studies on, e.g. the thermodynamic properties of the atmospheric organics, concentrations of low

  12. An explanation of flocculation using Lewis acid-base theory

    SciTech Connect

    Brown, P.M.; Stanley, D.A.; Scheiner, B.J.

    1988-01-01

    This paper describes a Bureau of Mines-devleoped method of dewatering clay slurries based on flocculation by high-molecular-weight polymers and water removal from the formed flocs using a trommel or hydrosieve. The exchange ion on the clays affects their dewaterability. Metal ions in solution and on the exchange sites of smectite clays are known to act as Lewis acids. Recent work has determined that these ions can be titrated with high-molecular-weight polymers. The relative acidity of the exchange ion and the basicity of the polymer determined by the new method give insight into the dewatering mechanism.

  13. [Participation of the adrenals in the pathogenesis of metabolic acid-base disorders].

    PubMed

    Iluchev, D; Shtereva, S

    1976-01-01

    The authors examined in dynamics the changes in the functional state of the adrenals on 240 rabbits, which served as models for acute metabolic deviations in the acid-base balance. The obtained results showed that the acute metabolic acidosis increased moderately the values of ACTH and 17-hydroxycorticosteroids in blood without changing their concentration on the adrenal tissue. It lowered strongly the content of catecholamines (adrenaline and noradranaline) in the adrenal medular part. The metabolic alkalosis raised the concentration of ACTH in blood plasma and increased the amount of corticosteroids in blood and adrenals. There was no well formed parallelism in normalizing acid-base and hormonal indices. As a consequence of this a stage of postaciodotic catecholamine adrenal deficit was formed as well as metabasic hypercorticism in the experimental animals. PMID:14819

  14. Acid-base transport in pancreas—new challenges

    PubMed Central

    Novak, Ivana; Haanes, Kristian A.; Wang, Jing

    2013-01-01

    Along the gastrointestinal tract a number of epithelia contribute with acid or basic secretions in order to aid digestive processes. The stomach and pancreas are the most extreme examples of acid (H+) and base (HCO−3) transporters, respectively. Nevertheless, they share the same challenges of transporting acid and bases across epithelia and effectively regulating their intracellular pH. In this review, we will make use of comparative physiology to enlighten the cellular mechanisms of pancreatic HCO−3 and fluid secretion, which is still challenging physiologists. Some of the novel transporters to consider in pancreas are the proton pumps (H+-K+-ATPases), as well as the calcium-activated K+ and Cl− channels, such as KCa3.1 and TMEM16A/ANO1. Local regulators, such as purinergic signaling, fine-tune, and coordinate pancreatic secretion. Lastly, we speculate whether dys-regulation of acid-base transport contributes to pancreatic diseases including cystic fibrosis, pancreatitis, and cancer. PMID:24391597

  15. Correlation between the acid-base properties of the La2O3 catalyst and its methane reactivity.

    PubMed

    Chu, Changqing; Zhao, Yonghui; Li, Shenggang; Sun, Yuhan

    2016-06-28

    Density functional theory and coupled cluster theory calculations were carried out to study the effects of the acid-base properties of the La2O3 catalyst on its catalytic activity in the oxidative coupling of methane (OCM) reaction. The La(3+)-O(2-) pair site for CH4 activation is considered as a Lewis acid-Brönsted base pair. Using the Lewis acidity and the Brönsted basicity in the fluoride affinity and proton affinity scales as quantitative measures of the acid-base properties, the energy barrier for CH4 activation at the pair site can be linearly correlated with these acid-base properties. The pair site consisting of a strong Lewis acid La(3+) site and a strong Brönsted base O(2-) site is the most reactive for CH4 activation. In addition, the basicity of the La2O3 catalyst was traditionally measured by temperature-programmed desorption of CO2, but the CO2 chemisorption energy is better regarded as a combined measure of the acid-base properties of the pair site. A linear relationship of superior quality was found between the energy barrier for CH4 activation and the CO2 chemisorption energy, and the pair site favorable for CO2 chemisorption is also more reactive for CH4 activation, leading to the conflicting role of the "basicity" of the La2O3 catalyst in the OCM reaction. The necessity for very high reaction temperatures in the OCM reaction is rationalized by the requirement for the recovery of the most reactive acid-base pair site, which unfortunately also reacts most readily with the byproduct CO2 to form the very stable CO3(2-) species.

  16. Hydrodynamic Instabilities of Acid-Base Reaction Fronts: Active Role of a Color Indicator

    NASA Astrophysics Data System (ADS)

    Riolfo, L. A.; Almarcha, C.; Trevelyan, P. M. J.; El Hasi, C.; Zalts, A.; D'Onofrio, A.; de Wit, A.

    2010-11-01

    Chemical reactions are able to trigger hydrodynamic flows by, for example changing the density of the solutions across the reactive interfaces. In this work we present an experimental and theoretical study of the buoyancy-driven hydrodynamic instabilities that can occur when two miscible reactive solutions of an acid-base system are put in contact in the gravity field. We compare situations where a hydrochloric acid aqueous solution is put on top of a sodium hydroxide aqueous solution with or without a color indicator (Bromocresol Green). We also analyze the situation where a hydrochloric acid is put on top of an aqueous solution of a color indicator without any base. We show that the patterns observed and the instabilities taking place strongly depend on the presence of a color indicator. Using a reaction-diffusion model for the concentrations of all species (including the color indicator) we analyze the different possible sources of destabilization of the acid-base front and explain the various instabilities observed in each experimental system.

  17. Acid-base property of N-methylimidazolium-based protic ionic liquids depending on anion.

    PubMed

    Kanzaki, Ryo; Doi, Hiroyuki; Song, Xuedan; Hara, Shota; Ishiguro, Shin-ichi; Umebayashi, Yasuhiro

    2012-12-01

    Proton-donating and ionization properties of several protic ionic liquids (PILs) made from N-methylimidazole (Mim) and a series of acids (HA) have been assessed by means of potentiometric and calorimetric titrations. With regard to strong acids, bis(trifluoromethanesulfonyl) amide (Tf(2)NH) and trifluoromethanesulfonic acid (TfOH), it was elucidated that the two equimolar mixtures with Mim almost consist of ionic species, HMim(+) and A(-), and the proton transfer equilibrium corresponding to autoprotolysis in ordinary molecular liquids was established. The respective autoprotolysis constants were successfully evaluated, which indicate the proton-donating abilities of TfOH and Tf(2)NH in the respective PILs are similar. In the case of trifluoroacetic acid, the proton-donating ability of CF(3)COOH is much weaker than those of TfOH and Tf(2)NH, while ions are predominant species. On the other hand, with regard to formic acid and acetic acid, protons of these acids are suggested not to transfer to Mim sufficiently. From calorimetric titrations, about half of Mim is estimated to be proton-attached at most in the CH(3)COOH-Mim equimolar mixture. In such a mixture, hydrogen-bonding adducts formation has been suggested. The autoprotolysis constants of the present PILs show a good linear correlation with dissociation constants of the constituent acids in an aqueous phase.

  18. [Blood acid-base balance of sportsmen during physical activity].

    PubMed

    Petrushova, O P; Mikulyak, N I

    2014-01-01

    The aim of this study was to investigate the acid-base balance parameters in blood of sportsmen by physical activity. Before exercise lactate concentration in blood was normal. Carbon dioxide pressure (рСО2), bicarbonate concentration (НСО3 -), base excess (BE), were increased immediately after physical activity lactate concentration increased, while pH, BE, НСО3 -, рСО2 decreased in capillary blood of sportsmen. These changes show the development of lactate-acidosis which is partly compensated with bicarbonate buffering system and respiratory alkalosis. During postexercise recovery lactate concentration decreased, while рСО2, НСО3 -, BE increased. The results of this study can be used for diagnostics of acid-base disorders and their medical treatment for preservation of sportsmen physical capacity.

  19. PDMS-based gold electrode for sensing ascorbic acid.

    PubMed

    Xu, Qin; Bi, Lianhua; Zheng, Huxiang; Fan, Dahe; Wang, Wei

    2011-11-01

    Electrode with optical shapes is appreciated in microfluidics. In this article, we reported a flexible poly(dimethylsiloxane) (PDMS)-based gold electrode for ascorbic acid detection. Gold nanoparticles were chemically deposited on PDMS and the composite film was applied as working electrode. The electrode could undergo deformation and display good response performance without damage. This biosensor could give quick response to ascorbic acid (AA) (<5s) and the currents were linear with concentrations of AA in range of 0.023-7.00 mM and 30-100 mM, respectively. Limit of detection was 0.008 mM (S/N=3). This biosensor has been applied to determine ascorbic acid content in vitamin C tablets and the results were consistent with traditional iodometric method. PMID:21807485

  20. Food composition and acid-base balance: alimentary alkali depletion and acid load in herbivores.

    PubMed

    Kiwull-Schöne, Heidrun; Kiwull, Peter; Manz, Friedrich; Kalhoff, Hermann

    2008-02-01

    Alkali-enriched diets are recommended for humans to diminish the net acid load of their usual diet. In contrast, herbivores have to deal with a high dietary alkali impact on acid-base balance. Here we explore the role of nutritional alkali in experimentally induced chronic metabolic acidosis. Data were collected from healthy male adult rabbits kept in metabolism cages to obtain 24-h urine and arterial blood samples. Randomized groups consumed rabbit diets ad libitum, providing sufficient energy but variable alkali load. One subgroup (n = 10) received high-alkali food and approximately 15 mEq/kg ammonium chloride (NH4Cl) with its drinking water for 5 d. Another group (n = 14) was fed low-alkali food for 5 d and given approximately 4 mEq/kg NH4Cl daily for the last 2 d. The wide range of alimentary acid-base load was significantly reflected by renal base excretion, but normal acid-base conditions were maintained in the arterial blood. In rabbits fed a high-alkali diet, the excreted alkaline urine (pH(u) > 8.0) typically contained a large amount of precipitated carbonate, whereas in rabbits fed a low-alkali diet, both pH(u) and precipitate decreased considerably. During high-alkali feeding, application of NH4Cl likewise decreased pH(u), but arterial pH was still maintained with no indication of metabolic acidosis. During low-alkali feeding, a comparably small amount of added NH4Cl further lowered pH(u) and was accompanied by a significant systemic metabolic acidosis. We conclude that exhausted renal base-saving function by dietary alkali depletion is a prerequisite for growing susceptibility to NH4Cl-induced chronic metabolic acidosis in the herbivore rabbit.

  1. Acid-base titrations by stepwise addition of equal volumes of titrant with special reference to automatic titrations-II Theory of titration of mixtures of acids, polyprotic acids, acids in mixture with weak bases, and ampholytes.

    PubMed

    Pehrsson, L; Ingman, F; Johansson, S

    A general method for evaluating titration data for mixtures of acids and for acids in mixture with weak bases is presented. Procedures are given that do not require absolute [H]-data, i.e., relative [H]-data may be used. In most cases a very rough calibration of the electrode system is enough. Further, for simple systems, very approximate values of the stability constants are sufficient. As examples, the titration of the following are treated in some detail: a mixture of two acids, a diprotic acid, an acid in presence of its conjugate base, and an ampholyte.

  2. An injectable, low-toxicity phospholipid-based phase separation gel that induces strong and persistent immune responses in mice.

    PubMed

    Han, Lu; Xue, Jiao; Wang, Luyao; Peng, Ke; Zhang, Zhirong; Gong, Tao; Sun, Xun

    2016-10-01

    Sustained antigen delivery using incomplete Freund's adjuvant (IFA) can induce strong, long-term immune response, but it can also cause severe side effects. Here we describe an injectable, phospholipid-based phase separation gel (PPSG) that readily transforms in situ into a drug depot. PPSG loaded with the model antigen ovalbumin (OVA) supported sustained OVA release in mice that lasted nearly one month. Immunizing mice with a single injection of PPSG/OVA elicited a strong and persistent increase in titers of OVA-specific IgG, IgG1 and IgG2a. Co-administering CpG-ODN further increased antibody titers. Such co-administration recruited dendritic cells to injection sites and activated dendritic cells in the draining lymph nodes. Moreover, immunization with PPSG/OVA/CpG resulted in potent memory antibody responses and high frequency of memory T cells. Remarkably, PPSG/OVA/CpG was associated with much lower toxicity at injection sites than IFA/OVA/CpG, and it showed no systemic toxicity such as to lymph nodes or spleen. These findings illustrate the potential of injectable PPSG for sustained, minimally toxic delivery of antigens and adjuvants. PMID:27522253

  3. Chemical shifts assignments of the archaeal MC1 protein and a strongly bent 15 base pairs DNA duplex in complex.

    PubMed

    Loth, Karine; Landon, Céline; Paquet, Françoise

    2015-04-01

    MC1 is the most abundant architectural protein present in Methanosarcina thermophila CHTI55 in laboratory growth conditions and is structurally unrelated to other DNA-binding proteins. MC1 functions are to shape and to protect DNA against thermal denaturation by binding to it. Therefore, MC1 has a strong affinity for any double-stranded DNA. However, it recognizes and preferentially binds to bent DNA, such as four-way junctions and negatively supercoiled DNA minicircles. Combining NMR data, electron microscopy data, biochemistry, molecular modelisation and docking approaches, we proposed recently a new type of DNA/protein complex, in which the monomeric protein MC1 binds on the concave side of a strongly bent 15 base pairs DNA. We present here the NMR chemical shifts assignments of each partner in the complex, (1)H (15)N MC1 protein and (1)H (13)C (15)N bent duplex DNA, as first step towards the first experimental 3D structure of this new type of DNA/protein complex.

  4. Hard and soft acids and bases: structure and process.

    PubMed

    Reed, James L

    2012-07-01

    Under investigation is the structure and process that gives rise to hard-soft behavior in simple anionic atomic bases. That for simple atomic bases the chemical hardness is expected to be the only extrinsic component of acid-base strength, has been substantiated in the current study. A thermochemically based operational scale of chemical hardness was used to identify the structure within anionic atomic bases that is responsible for chemical hardness. The base's responding electrons have been identified as the structure, and the relaxation that occurs during charge transfer has been identified as the process giving rise to hard-soft behavior. This is in contrast the commonly accepted explanations that attribute hard-soft behavior to varying degrees of electrostatic and covalent contributions to the acid-base interaction. The ability of the atomic ion's responding electrons to cause hard-soft behavior has been assessed by examining the correlation of the estimated relaxation energies of the responding electrons with the operational chemical hardness. It has been demonstrated that the responding electrons are able to give rise to hard-soft behavior in simple anionic bases.

  5. Model for acid-base chemistry in nanoparticle growth (MABNAG)

    NASA Astrophysics Data System (ADS)

    Yli-Juuti, T.; Barsanti, K.; Hildebrandt Ruiz, L.; Kieloaho, A.-J.; Makkonen, U.; Petäjä, T.; Ruuskanen, T.; Kulmala, M.; Riipinen, I.

    2013-12-01

    Climatic effects of newly-formed atmospheric secondary aerosol particles are to a large extent determined by their condensational growth rates. However, all the vapours condensing on atmospheric nanoparticles and growing them to climatically relevant sizes are not identified yet and the effects of particle phase processes on particle growth rates are poorly known. Besides sulfuric acid, organic compounds are known to contribute significantly to atmospheric nanoparticle growth. In this study a particle growth model MABNAG (Model for Acid-Base chemistry in NAnoparticle Growth) was developed to study the effect of salt formation on nanoparticle growth, which has been proposed as a potential mechanism lowering the equilibrium vapour pressures of organic compounds through dissociation in the particle phase and thus preventing their evaporation. MABNAG is a model for monodisperse aqueous particles and it couples dynamics of condensation to particle phase chemistry. Non-zero equilibrium vapour pressures, with both size and composition dependence, are considered for condensation. The model was applied for atmospherically relevant systems with sulfuric acid, one organic acid, ammonia, one amine and water in the gas phase allowed to condense on 3-20 nm particles. The effect of dissociation of the organic acid was found to be small under ambient conditions typical for a boreal forest site, but considerable for base-rich environments (gas phase concentrations of about 1010 cm-3 for the sum of the bases). The contribution of the bases to particle mass decreased as particle size increased, except at very high gas phase concentrations of the bases. The relative importance of amine versus ammonia did not change significantly as a function of particle size. While our results give a reasonable first estimate on the maximum contribution of salt formation to nanoparticle growth, further studies on, e.g. the thermodynamic properties of the atmospheric organics, concentrations of low

  6. Strong Surface Treatment Effects on Reinforcement Efficiency in Biocomposites Based on Cellulose Nanocrystals in Poly(vinyl acetate) Matrix.

    PubMed

    Ansari, Farhan; Salajková, Michaela; Zhou, Qi; Berglund, Lars A

    2015-12-14

    In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.

  7. A strong-field driver in the single-cycle regime based on self-compression in a kagome fibre

    PubMed Central

    Balciunas, T.; Fourcade-Dutin, C.; Fan, G.; Witting, T.; Voronin, A. A.; Zheltikov, A. M.; Gerome, F.; Paulus, G. G.; Baltuska, A.; Benabid, F.

    2015-01-01

    Over the past decade intense laser fields with a single-cycle duration and even shorter, subcycle multicolour field transients have been generated and applied to drive attosecond phenomena in strong-field physics. Because of their extensive bandwidth, single-cycle fields cannot be emitted or amplified by laser sources directly and, as a rule, are produced by external pulse compression—a combination of nonlinear optical spectral broadening followed up by dispersion compensation. Here we demonstrate a simple robust driver for high-field applications based on this Kagome fibre approach that ensures pulse self-compression down to the ultimate single-cycle limit and provides phase-controlled pulses with up to a 100 μJ energy level, depending on the filling gas, pressure and the waveguide length. PMID:25625549

  8. A mathematical model of pH, based on the total stoichiometric concentration of acids, bases and ampholytes dissolved in water.

    PubMed

    Mioni, Roberto; Mioni, Giuseppe

    2015-10-01

    In chemistry and in acid-base physiology, the Henderson-Hasselbalch equation plays a pivotal role in studying the behaviour of the buffer solutions. However, it seems that the general function to calculate the valence of acids, bases and ampholytes, N = f(pH), at any pH, has only been provided by Kildeberg. This equation can be applied to strong acids and bases, pluriprotic weak acids, bases and ampholytes, with an arbitrary number of acid strength constants, pKA, including water. By differentiating this function with respect to pH, we obtain the general equation for the buffer value. In addition, by integrating the titration curve, TA, proposed by Kildeberg, and calculating its Legendre transform, we obtain the Gibbs free energy of pH (or pOH)-dependent titratable acid. Starting from the law of electroneutrality and applying suitable simplifications, it is possible to calculate the pH of the buffer solutions by numerical methods, available in software packages such as Excel. The concept of buffer capacity has also been clarified by Urbansky, but, at variance with our approach, not in an organic manner. In fact, for each set of monobasic, dibasic, tribasic acids, etc., various equations are presented which independently fit each individual acid-base category. Consequently, with the increase in acid groups (pKA), the equations become more and more difficult, both in practice and in theory. Some examples are proposed to highlight the boundary that exists between acid-base physiology and the thermodynamic concepts of energy, chemical potential, amount of substance and acid resistance. PMID:26059505

  9. A mathematical model of pH, based on the total stoichiometric concentration of acids, bases and ampholytes dissolved in water.

    PubMed

    Mioni, Roberto; Mioni, Giuseppe

    2015-10-01

    In chemistry and in acid-base physiology, the Henderson-Hasselbalch equation plays a pivotal role in studying the behaviour of the buffer solutions. However, it seems that the general function to calculate the valence of acids, bases and ampholytes, N = f(pH), at any pH, has only been provided by Kildeberg. This equation can be applied to strong acids and bases, pluriprotic weak acids, bases and ampholytes, with an arbitrary number of acid strength constants, pKA, including water. By differentiating this function with respect to pH, we obtain the general equation for the buffer value. In addition, by integrating the titration curve, TA, proposed by Kildeberg, and calculating its Legendre transform, we obtain the Gibbs free energy of pH (or pOH)-dependent titratable acid. Starting from the law of electroneutrality and applying suitable simplifications, it is possible to calculate the pH of the buffer solutions by numerical methods, available in software packages such as Excel. The concept of buffer capacity has also been clarified by Urbansky, but, at variance with our approach, not in an organic manner. In fact, for each set of monobasic, dibasic, tribasic acids, etc., various equations are presented which independently fit each individual acid-base category. Consequently, with the increase in acid groups (pKA), the equations become more and more difficult, both in practice and in theory. Some examples are proposed to highlight the boundary that exists between acid-base physiology and the thermodynamic concepts of energy, chemical potential, amount of substance and acid resistance.

  10. Acid-base chemical mechanism of aspartase from Hafnia alvei.

    PubMed

    Yoon, M Y; Thayer-Cook, K A; Berdis, A J; Karsten, W E; Schnackerz, K D; Cook, P F

    1995-06-20

    An acid-base chemical mechanism is proposed for Hafnia alvei aspartase in which a proton is abstracted from C-3 of the monoanionic form of L-aspartate by an enzyme general base with a pK of 6.3-6.6 in the absence and presence of Mg2+. The resulting carbanion is presumably stabilized by delocalization of electrons into the beta-carboxyl with the assistance of a protonated enzyme group in the vicinity of the beta-carboxyl. Ammonia is then expelled with the assistance of a general acid group that traps an initially expelled NH3 as the final NH4+ product. In agreement with the function of the general acid group, potassium, an analog of NH4+, binds optimally when the group is unprotonated. The pK for the general acid is about 7 in the absence of Mg2+, but is increased by about a pH unit in the presence of Mg2+. Since the same pK values are observed in the pKi(succinate) and V/K pH profile, both enzyme groups must be in their optimum protonation state for efficient binding of reactant in the presence of Mg2+. At the end of a catalytic cycle, both the general base and general acid groups are in a protonation state opposite that in which they started when aspartate was bound. The presence of Mg2+ causes a pH-dependent activation of aspartase exhibited as a partial change in the V and V/Kasp pH profiles. When the aspartase reaction is run in D2O to greater than 50% completion no deuterium is found in the remaining aspartate, indicating that the site is inaccessible to solvent during the catalytic cycle.

  11. Bio-based production of organic acids with Corynebacterium glutamicum.

    PubMed

    Wieschalka, Stefan; Blombach, Bastian; Bott, Michael; Eikmanns, Bernhard J

    2013-03-01

    The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, L- and D-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers. PMID:23199277

  12. Bio-based production of organic acids with Corynebacterium glutamicum.

    PubMed

    Wieschalka, Stefan; Blombach, Bastian; Bott, Michael; Eikmanns, Bernhard J

    2013-03-01

    The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, L- and D-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers.

  13. Selective separation and purification of highly polar basic compounds using a silica-based strong cation exchange stationary phase.

    PubMed

    Long, Zhen; Guo, Zhimou; Xue, Xingya; Zhang, Xiuli; Nordahl, Lilly; Liang, Xinmiao

    2013-12-01

    Compared to moderately and weakly hydrophilic bases, highly polar basic compounds are even more difficult to separate due to their poor retention in reversed phase (RP) mode. This study described the successful applications of a strong cation exchange (SCX) stationary phase to achieve symmetric peak shape, adequate retention and selectivity in the separation of very polar basic compounds. Salt and acetonitrile concentrations were adjusted to optimize the separation. Good correlations (R(2)=0.998-1.000) between the logarithm of the retention factor and the logarithm of salt or acetonitrile concentration were obtained. Gradients generated by changing salt or acetonitrile concentration were compared for the analysis of different highly polar bases. Although all of the analytes were eluted more quickly with an acetonitrile gradient, the effect of the gradients tested on peak width and peak shape varied with respect to analyte. In addition, the effects of different types of cation and anion additives were also investigated. After separation parameters were acquired, the SCX-based method was utilized to analyze highly hydrophilic alkaloids from Scopolia tangutica Maxim with high separation efficiency (plate numbers>32,000 m(-1)). Concurrently, one very polar alkaloid fraction was purified with symmetric peak shape using the current method. Our results suggest that SCX stationary phase can be used as an alternative to RP stationary phase in the analysis and purification of highly hydrophilic basic compounds. PMID:24267097

  14. The physiological assessment of acid-base balance.

    PubMed

    Howorth, P J

    1975-04-01

    Acid-base terminology including the sue of SI units is reviewed. The historical reasons why nomograms have been particularly used in acid-base work are discussed. The theoretical basis of the Henderson-Hasselbalch equation is considered. It is emphasized that the solubility of CO2 in plasma and the apparent first dissociation constant of carbonic acid are not chemical constants when applied to media of uncertain and varying composition such as blood plasma. The use of the Henderson-Hasselbalch equation in making hypothermia corrections for PCO2 is discussed. The Astrup system for the in vitro determination of blood gases and derived parameters is described and the theoretical weakness of the base excess concept stressed. A more clinically-oriented approach to the assessment of acid-base problems is presented. Measurement of blood [H+] and PCO2 are considered to be primary data which should be recorded on a chart with in vivo CO2-titration lines (see below). Clinical information and results of other laboratory investigations such as plasma bicarbonate, PO2,P50 are then to be considered together with the primary data. In order to interpret this combined information it is essential to take into account the known ventilatory response to metabolic acidosis and alkalosis, and the renal response to respiratory acidosis and alkalosis. The use is recommended of a chart showing the whole-body CO2-titration points obtained when patients with different initial levels of non-respiratory [H+] are ventilated. A number of examples are given of the use of this [H+] and PCO2 in vivo chart in the interpretation of acid-base data. The aetiology, prognosis and treatment of metabolic alkalosis is briefly reviewed. Treatment with intravenous acid is recommended for established cases. Attention is drawn to the possibility of iatrogenic production of metabolic alkalosis. Caution is expressed over the use of intravenous alkali in all but the severest cases of metabolic acidosis. The role of

  15. The FKBP-rapamycin binding domain of human TOR undergoes strong conformational changes in the presence of membrane mimetics with and without the regulator phosphatidic acid.

    PubMed

    Rodriguez Camargo, Diana C; Link, Nina M; Dames, Sonja A

    2012-06-19

    The Ser/Thr kinase target of rapamycin (TOR) is a central controller of cellular growth and metabolism. Misregulation of TOR signaling is involved in metabolic and neurological disorders and tumor formation. TOR can be inhibited by association of a complex of rapamycin and FKBP12 to the FKBP12-rapamycin binding (FRB) domain. This domain was further proposed to interact with phosphatidic acid (PA), a lipid second messenger present in cellular membranes. Because mammalian TOR has been localized at various cellular membranes and in the nucleus, the output of TOR signaling may depend on its localization, which is expected to be influenced by the interaction with complex partners and regulators in response to cellular signals. Here, we present a detailed characterization of the interaction of the FRB domain with PA and how it is influenced by the surrounding membrane environment. On the basis of nuclear magnetic resonance- and circular dichroism-monitored binding studies using different neutral and negatively charged lipids as well as different membrane mimetics (micelles, bicelles, and liposomes), the FRB domain may function as a conditional peripheral membrane protein. However, the data for the isolated domain just indicate an increased affinity for negatively charged lipids and membrane patches but no specific preference for PA or PA-enriched regions. The membrane-mimetic environment induces strong conformational changes that largely maintain the α-helical secondary structure content but presumably disperse the helices in the lipidic environment. Consistent with overlapping binding surfaces for different lipids and the FKBP12-rapamycin complex, binding of the inhibitor complex protects the FRB domain from interactions with membrane mimetics at lower lipid concentrations.

  16. Impact of nucleic acid self-alignment in a strong magnetic field on the interpretation of indirect spin-spin interactions.

    PubMed

    Vavřinská, Andrea; Zelinka, Jiří; Šebera, Jakub; Sychrovský, Vladimír; Fiala, Radovan; Boelens, Rolf; Sklenář, Vladimír; Trantírek, Lukáš

    2016-01-01

    Heteronuclear and homonuclear direct (D) and indirect (J) spin-spin interactions are important sources of structural information about nucleic acids (NAs). The Hamiltonians for the D and J interactions have the same functional form; thus, the experimentally measured apparent spin-spin coupling constant corresponds to a sum of J and D. In biomolecular NMR studies, it is commonly presumed that the dipolar contributions to Js are effectively canceled due to random molecular tumbling. However, in strong magnetic fields, such as those employed for NMR analysis, the tumbling of NA fragments is anisotropic because the inherent magnetic susceptibility of NAs causes an interaction with the external magnetic field. This motional anisotropy is responsible for non-zero D contributions to Js. Here, we calculated the field-induced D contributions to 33 structurally relevant scalar coupling constants as a function of magnetic field strength, temperature and NA fragment size. We identified two classes of Js, namely (1)JCH and (3)JHH couplings, whose quantitative interpretation is notably biased by NA motional anisotropy. For these couplings, the magnetic field-induced dipolar contributions were found to exceed the typical experimental error in J-coupling determinations by a factor of two or more and to produce considerable over- or under-estimations of the J coupling-related torsion angles, especially at magnetic field strengths >12 T and for NA fragments longer than 12 bp. We show that if the non-zero D contributions to J are not properly accounted for, they might cause structural artifacts/bias in NA studies that use solution NMR spectroscopy. PMID:26685997

  17. Impact of nucleic acid self-alignment in a strong magnetic field on the interpretation of indirect spin-spin interactions.

    PubMed

    Vavřinská, Andrea; Zelinka, Jiří; Šebera, Jakub; Sychrovský, Vladimír; Fiala, Radovan; Boelens, Rolf; Sklenář, Vladimír; Trantírek, Lukáš

    2016-01-01

    Heteronuclear and homonuclear direct (D) and indirect (J) spin-spin interactions are important sources of structural information about nucleic acids (NAs). The Hamiltonians for the D and J interactions have the same functional form; thus, the experimentally measured apparent spin-spin coupling constant corresponds to a sum of J and D. In biomolecular NMR studies, it is commonly presumed that the dipolar contributions to Js are effectively canceled due to random molecular tumbling. However, in strong magnetic fields, such as those employed for NMR analysis, the tumbling of NA fragments is anisotropic because the inherent magnetic susceptibility of NAs causes an interaction with the external magnetic field. This motional anisotropy is responsible for non-zero D contributions to Js. Here, we calculated the field-induced D contributions to 33 structurally relevant scalar coupling constants as a function of magnetic field strength, temperature and NA fragment size. We identified two classes of Js, namely (1)JCH and (3)JHH couplings, whose quantitative interpretation is notably biased by NA motional anisotropy. For these couplings, the magnetic field-induced dipolar contributions were found to exceed the typical experimental error in J-coupling determinations by a factor of two or more and to produce considerable over- or under-estimations of the J coupling-related torsion angles, especially at magnetic field strengths >12 T and for NA fragments longer than 12 bp. We show that if the non-zero D contributions to J are not properly accounted for, they might cause structural artifacts/bias in NA studies that use solution NMR spectroscopy.

  18. Acid and base stress and transcriptomic responses in Bacillus subtilis.

    PubMed

    Wilks, Jessica C; Kitko, Ryan D; Cleeton, Sarah H; Lee, Grace E; Ugwu, Chinagozi S; Jones, Brian D; BonDurant, Sandra S; Slonczewski, Joan L

    2009-02-01

    Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K(+)/H(+) antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids.

  19. Hydrogen bonded supramolecular structures of eight organic salts based on 2,6-diaminopyridine, and organic acids

    NASA Astrophysics Data System (ADS)

    Jin, Shouwen; Zhao, Ying; Liu, Bin; Jin, Xiunan; Zhang, Huan; Wen, Xianhong; Liu, Hui; Jin, Li; Wang, Daqi

    2015-11-01

    Here anhydrous and hydrated multi-component organic acid-base salts of 2,6-diaminopyridine have been prepared with the organic acids as trichloroacetic acid, 3,5-dinitrobenzoic acid, 5-nitrosalicylic acid, 3,5-dihydroxybenzoic acid, 5-sulfosalicylic acid, m-phthalic acid, naphthalene-1,5-disulfonic acid, and glutaric acid. The eight crystalline compounds were characterized by X-ray diffraction analysis, infrared (IR), melting point (mp), and elemental analysis. Except salt 4, all structures adopted the hetero R22(8) supramolecular synthon. There were extensive N-H···O/O-H···O/N-H···N/N-H···S hydrogen bonds as well as CH···O, CH-N, CH-π, NH-π, π-π, C-π, Cl-O, and O-O interactions in the supramolecular architectures. The combination of these weak and strong hydrogen bonding associations in the crystal packing led to the formation of the 2D/3D structures.

  20. Acid-base properties of bentonite rocks with different origins.

    PubMed

    Nagy, Noémi M; Kónya, József

    2006-03-01

    Five bentonite samples (35-47% montmorillonite) from a Sarmatian sediment series with bentonite sites around Sajóbábony (Hungary) is studied. Some of these samples were tuffogenic bentonite (sedimentary), the others were bentonitized tuff with volcano sedimentary origin. The acid-base properties of the edge sites were studied by potentiometric titrations and surface complexation modeling. It was found that the number and the ratio of silanol and aluminol sites as well as the intrinsic stability constants are different for the sedimentary bentonite and bentonitized tuff. The characteristic properties of the edges sites depend on the origins. The acid-base properties are compared to other commercial and standard bentonites.

  1. Evolution of the Acid-Base Status in Cardiac Arrest

    PubMed Central

    Carrasco G., Hugo A.; Oletta L., José F.

    1973-01-01

    In a study of the evolution of acid-base status in 26 patients who had cardiopulmonary arrest in the operating room, it appeared that: The determination of acid-base status within the first hour post-cardiac arrest is useful in differentiating final survivors from non-survivors. Respiratory or combined acidosis carries a poor prognosis not evidenced for metabolic acidosis. Late respiratory complications are more frequent in patients with initial combined acidosis. Treatment should be instituted on the basis of frequent determinations of acidbase status, since accurate diagnosis of degree and type of acidosis cannot be done on clinical grounds only. Recovery of consciousness is influenced by the type and severity of acidosis, less so by duration of arrest; and that high pCO2 is associated frequently with unconsciousness after recovery of circulatory function. PMID:4709532

  2. Self-glazing ceramic tiles based on acidic igneous glasses

    SciTech Connect

    Merkin, A.P.; Nanazashvili, V.I.

    1988-07-01

    A technology was derived to produce self-glazing ceramic tiles based on single-component systems of acidic igneous (volcanic) glasses. A weakly alkaline solution of NaOH or KOH was used as the sealing water to activate the sintering process. Tests conducted on the self-glazing ceramic tiles showed that their water absorption amounts to 2.5-8%, linear shrinkage is 3.2-7%, and frost resistance amounts to 35-70 cycles. The application of acidic igneous glasses as the main raw material for the production of ceramic facing tiles made it possible to widen the raw material base and simplify the technology for fabricating ceramic facing tiles at lower cost. The use of waste products when processing perlite-bearing rocks, when carrying out mining and cutting of tuffs, slags, and tuff breccia for recovering cut materials was recommended.

  3. Has Stewart approach improved our ability to diagnose acid-base disorders in critically ill patients?

    PubMed

    Masevicius, Fabio D; Dubin, Arnaldo

    2015-02-01

    The Stewart approach-the application of basic physical-chemical principles of aqueous solutions to blood-is an appealing method for analyzing acid-base disorders. These principles mainly dictate that pH is determined by three independent variables, which change primarily and independently of one other. In blood plasma in vivo these variables are: (1) the PCO2; (2) the strong ion difference (SID)-the difference between the sums of all the strong (i.e., fully dissociated, chemically nonreacting) cations and all the strong anions; and (3) the nonvolatile weak acids (Atot). Accordingly, the pH and the bicarbonate levels (dependent variables) are only altered when one or more of the independent variables change. Moreover, the source of H(+) is the dissociation of water to maintain electroneutrality when the independent variables are modified. The basic principles of the Stewart approach in blood, however, have been challenged in different ways. First, the presumed independent variables are actually interdependent as occurs in situations such as: (1) the Hamburger effect (a chloride shift when CO2 is added to venous blood from the tissues); (2) the loss of Donnan equilibrium (a chloride shift from the interstitium to the intravascular compartment to balance the decrease of Atot secondary to capillary leak; and (3) the compensatory response to a primary disturbance in either independent variable. Second, the concept of water dissociation in response to changes in SID is controversial and lacks experimental evidence. In addition, the Stewart approach is not better than the conventional method for understanding acid-base disorders such as hyperchloremic metabolic acidosis secondary to a chloride-rich-fluid load. Finally, several attempts were performed to demonstrate the clinical superiority of the Stewart approach. These studies, however, have severe methodological drawbacks. In contrast, the largest study on this issue indicated the interchangeability of the Stewart and

  4. [Injuries caused by acids and bases - emergency treatment].

    PubMed

    Reifferscheid, Florian; Stuhr, Markus; Kaiser, Guido; Freudenberg, Matthias; Kerner, Thoralf

    2014-06-01

    Emergency medical care for injuries caused by acids and bases is challenging for rescue services. They have to deal with operational safety, detection of the toxic agent, emergency medical care of the patient and handling of the rescue mission. Because of the rareness of such situations experience and routine are largely missing. This article highlights some basic points for the therapy and provides support for such rescue missions.

  5. Synthesis of bio-based methacrylic acid by decarboxylation of itaconic acid and citric acid catalyzed by solid transition-metal catalysts.

    PubMed

    Le Nôtre, Jérôme; Witte-van Dijk, Susan C M; van Haveren, Jacco; Scott, Elinor L; Sanders, Johan P M

    2014-09-01

    Methacrylic acid, an important monomer for the plastics industry, was obtained in high selectivity (up to 84%) by the decarboxylation of itaconic acid using heterogeneous catalysts based on Pd, Pt and Ru. The reaction takes place in water at 200-250 °C without any external added pressure, conditions significantly milder than those described previously for the same conversion with better yield and selectivity. A comprehensive study of the reaction parameters has been performed, and the isolation of methacrylic acid was achieved in 50% yield. The decarboxylation procedure is also applicable to citric acid, a more widely available bio-based feedstock, and leads to the production of methacrylic acid in one pot in 41% selectivity. Aconitic acid, the intermediate compound in the pathway from citric acid to itaconic acid was also used successfully as a substrate. PMID:25045161

  6. Influence of ions on aqueous acid-base reactions.

    PubMed

    Cox, M Jocelyn; Siwick, Bradley J; Bakker, Huib J

    2009-01-12

    We study the effects of bromide salts on the rate and mechanism of the aqueous proton/deuteron-transfer reaction between the photoacid 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS) and the base acetate. The proton/deuteron release is triggered by exciting HPTS with 400 nm femtosecond laser pulses. Probing the electronic and vibrational resonances of the photoacid, the conjugate photobase, the hydrated proton/deuteron and the accepting base with femtosecond visible and mid-infrared pulses monitors the proton transfer. Two reaction channels are identified: 1) direct long-range proton transfer over hydrogen-bonded water bridges that connect the acid and base and 2) acid dissociation to produce fully solvated protons followed by proton scavenging from solution by acetate. We observe that the addition of salt affects the long-range reaction pathway, and reduces both the rate at which protons are released to solution by HPTS and the rate at which solvated protons are scavenged from solution by acetate. We study the dependence of these effects on the nature and concentration of the dissolved salt.

  7. Interpretation of pH-activity profiles for acid-base catalysis from molecular simulations.

    PubMed

    Dissanayake, Thakshila; Swails, Jason M; Harris, Michael E; Roitberg, Adrian E; York, Darrin M

    2015-02-17

    The measurement of reaction rate as a function of pH provides essential information about mechanism. These rates are sensitive to the pK(a) values of amino acids directly involved in catalysis that are often shifted by the enzyme active site environment. Experimentally observed pH-rate profiles are usually interpreted using simple kinetic models that allow estimation of "apparent pK(a)" values of presumed general acid and base catalysts. One of the underlying assumptions in these models is that the protonation states are uncorrelated. In this work, we introduce the use of constant pH molecular dynamics simulations in explicit solvent (CpHMD) with replica exchange in the pH-dimension (pH-REMD) as a tool to aid in the interpretation of pH-activity data of enzymes and to test the validity of different kinetic models. We apply the methods to RNase A, a prototype acid-base catalyst, to predict the macroscopic and microscopic pK(a) values, as well as the shape of the pH-rate profile. Results for apo and cCMP-bound RNase A agree well with available experimental data and suggest that deprotonation of the general acid and protonation of the general base are not strongly coupled in transphosphorylation and hydrolysis steps. Stronger coupling, however, is predicted for the Lys41 and His119 protonation states in apo RNase A, leading to the requirement for a microscopic kinetic model. This type of analysis may be important for other catalytic systems where the active forms of the implicated general acid and base are oppositely charged and more highly correlated. These results suggest a new way for CpHMD/pH-REMD simulations to bridge the gap with experiments to provide a molecular-level interpretation of pH-activity data in studies of enzyme mechanisms.

  8. PSHA for Strong Ground-Motion Hazards in Marmara Region, Turkey with Physically-based Ground Motion Prediction Methodology

    NASA Astrophysics Data System (ADS)

    Mert, A.; Fahjan, Y.; Hutchings, L. J.

    2014-12-01

    We perform a probabilistic seismic hazard analysis (PSHA) for strong ground motion within the Marmara region, Turkey, from potential earthquakes along the North Anatolian fault segments in and around Marmara Sea. Because of the increasing awareness of earthquake threat in the Marmara Region, the need for seismic hazard studies has become progressively more important for planning risk reduction actions. We perform the PSHA utilizing empirical Green's functions (EGFs) along with models of finite rupture in place of standard "attenuation relations". The important aspect of this study is that we combined the basic PSHA with ground motion simulations and obtained hazard analysis for all significant magnitude earthquakes, and provide the necessary full-waveform simulated ground motions to calculate building response, and thus risk. Recordings of small earthquakes from a local seismic array operated by Kandilli Observatory and Earthquake Research Institute (KOERI) were used as EGFs. Over the past 50 years, probabilistic seismic hazard analysis (PSHA) has been based upon estimating annual frequency of exceedance for a ground-motion parameter at a particular site (i.e., a hazard curve, Cornell, 1968). In the present study, we estimated the seismic hazard in Marmara Region and we expand and utilize the "physically based" approach proposed by Hutchings et al. (2007), Scognamiglio and Hutchings (2009). This approach replaces the aleatory uncertainty that current PSHA studies estimate by regression of empirical parameters with epistemic uncertainty that is expressed by the variability in the physical parameters of earthquake rupture. Epistemic uncertainty can be reduced by further research. By 'physically based' we refer to ground motion synthesized with quasi-dynamic rupture models derived from physics and an understanding of earthquake process. This methodology provides source- and site-specific calculations of full-waveform ground motion time histories, which is important

  9. The normal acid-base status of mice.

    PubMed

    Iversen, Nina K; Malte, Hans; Baatrup, Erik; Wang, Tobias

    2012-03-15

    Rodent models are commonly used for various physiological studies including acid-base regulation. Despite the widespread use of especially genetic modified mice, little attention have been made to characterise the normal acid-base status in these animals in order to reveal proper control values. Furthermore, several studies report blood gas values obtained in anaesthetised animals. We, therefore, decided to characterise blood CO(2) binding characteristic of mouse blood in vitro and to characterise normal acid-base status in conscious BALBc mice. In vitro CO(2) dissociation curves, performed on whole blood equilibrated to various PCO₂ levels in rotating tonometers, revealed a typical mammalian pK' (pK'=7.816-0.234 × pH (r=0.34)) and a non-bicarbonate buffer capacity (16.1 ± 2.6 slyke). To measure arterial acid-base status, small blood samples were taken from undisturbed mice with indwelling catheters in the carotid artery. In these animals, pH was 7.391 ± 0.026, plasma [HCO(3)(-)] 18.4 ± 0.83 mM, PCO₂ 30.3 ± 2.1 mm Hg and lactate concentration 4.6 ± 0.7 mM. Our study, therefore, shows that mice have an arterial pH that resembles other mammals, although arterial PCO₂ tends to be lower than in larger mammals. However, pH from arterial blood sampled from mice anaesthetised with isoflurane was significantly lower (pH 7.239 ± 0.021), while plasma [HCO(3)(-)] was 18.5 ± 1.4 mM, PCO₂ 41.9 ± 2.9 mm Hg and lactate concentration 4.48 ± 0.67 mM. Furthermore, we measured metabolism and ventilation (V(E)) in order to determine the ventilation requirements (VE/VO₂) to answer whether small mammals tend to hyperventilate. We recommend, therefore, that studies on acid-base regulation in mice should be based on samples taken for indwelling catheters rather than cardiac puncture of terminally anaesthetised mice.

  10. Lewis base activation of Lewis acids: development of a Lewis base catalyzed selenolactonization.

    PubMed

    Denmark, Scott E; Collins, William R

    2007-09-13

    The concept of Lewis base activation of Lewis acids has been applied to the selenolactonization reaction. Through the use of substoichiometric amounts of Lewis bases with "soft" donor atoms (S, Se, P) significant rate enhancements over the background reaction are seen. Preliminary mechanistic investigations have revealed the resting state of the catalyst as well as the significance of a weak Brønsted acid promoter.

  11. Fault Diagnosis for the Heat Exchanger of the Aircraft Environmental Control System Based on the Strong Tracking Filter

    PubMed Central

    Ma, Jian; Lu, Chen; Liu, Hongmei

    2015-01-01

    The aircraft environmental control system (ECS) is a critical aircraft system, which provides the appropriate environmental conditions to ensure the safe transport of air passengers and equipment. The functionality and reliability of ECS have received increasing attention in recent years. The heat exchanger is a particularly significant component of the ECS, because its failure decreases the system’s efficiency, which can lead to catastrophic consequences. Fault diagnosis of the heat exchanger is necessary to prevent risks. However, two problems hinder the implementation of the heat exchanger fault diagnosis in practice. First, the actual measured parameter of the heat exchanger cannot effectively reflect the fault occurrence, whereas the heat exchanger faults are usually depicted by utilizing the corresponding fault-related state parameters that cannot be measured directly. Second, both the traditional Extended Kalman Filter (EKF) and the EKF-based Double Model Filter have certain disadvantages, such as sensitivity to modeling errors and difficulties in selection of initialization values. To solve the aforementioned problems, this paper presents a fault-related parameter adaptive estimation method based on strong tracking filter (STF) and Modified Bayes classification algorithm for fault detection and failure mode classification of the heat exchanger, respectively. Heat exchanger fault simulation is conducted to generate fault data, through which the proposed methods are validated. The results demonstrate that the proposed methods are capable of providing accurate, stable, and rapid fault diagnosis of the heat exchanger. PMID:25823010

  12. Fault diagnosis for the heat exchanger of the aircraft environmental control system based on the strong tracking filter.

    PubMed

    Ma, Jian; Lu, Chen; Liu, Hongmei

    2015-01-01

    The aircraft environmental control system (ECS) is a critical aircraft system, which provides the appropriate environmental conditions to ensure the safe transport of air passengers and equipment. The functionality and reliability of ECS have received increasing attention in recent years. The heat exchanger is a particularly significant component of the ECS, because its failure decreases the system's efficiency, which can lead to catastrophic consequences. Fault diagnosis of the heat exchanger is necessary to prevent risks. However, two problems hinder the implementation of the heat exchanger fault diagnosis in practice. First, the actual measured parameter of the heat exchanger cannot effectively reflect the fault occurrence, whereas the heat exchanger faults are usually depicted by utilizing the corresponding fault-related state parameters that cannot be measured directly. Second, both the traditional Extended Kalman Filter (EKF) and the EKF-based Double Model Filter have certain disadvantages, such as sensitivity to modeling errors and difficulties in selection of initialization values. To solve the aforementioned problems, this paper presents a fault-related parameter adaptive estimation method based on strong tracking filter (STF) and Modified Bayes classification algorithm for fault detection and failure mode classification of the heat exchanger, respectively. Heat exchanger fault simulation is conducted to generate fault data, through which the proposed methods are validated. The results demonstrate that the proposed methods are capable of providing accurate, stable, and rapid fault diagnosis of the heat exchanger.

  13. Fault diagnosis for the heat exchanger of the aircraft environmental control system based on the strong tracking filter.

    PubMed

    Ma, Jian; Lu, Chen; Liu, Hongmei

    2015-01-01

    The aircraft environmental control system (ECS) is a critical aircraft system, which provides the appropriate environmental conditions to ensure the safe transport of air passengers and equipment. The functionality and reliability of ECS have received increasing attention in recent years. The heat exchanger is a particularly significant component of the ECS, because its failure decreases the system's efficiency, which can lead to catastrophic consequences. Fault diagnosis of the heat exchanger is necessary to prevent risks. However, two problems hinder the implementation of the heat exchanger fault diagnosis in practice. First, the actual measured parameter of the heat exchanger cannot effectively reflect the fault occurrence, whereas the heat exchanger faults are usually depicted by utilizing the corresponding fault-related state parameters that cannot be measured directly. Second, both the traditional Extended Kalman Filter (EKF) and the EKF-based Double Model Filter have certain disadvantages, such as sensitivity to modeling errors and difficulties in selection of initialization values. To solve the aforementioned problems, this paper presents a fault-related parameter adaptive estimation method based on strong tracking filter (STF) and Modified Bayes classification algorithm for fault detection and failure mode classification of the heat exchanger, respectively. Heat exchanger fault simulation is conducted to generate fault data, through which the proposed methods are validated. The results demonstrate that the proposed methods are capable of providing accurate, stable, and rapid fault diagnosis of the heat exchanger. PMID:25823010

  14. Characterization of Strong Promoters from an Environmental Flavobacterium hibernum Strain by Using a Green Fluorescent Protein-Based Reporter System▿

    PubMed Central

    Chen, S.; Bagdasarian, M.; Kaufman, M. G.; Walker, E. D.

    2007-01-01

    We developed techniques for the genetic manipulation of Flavobacterium species and used it to characterize several promoters found in these bacteria. Our studies utilized Flavobacterium hibernum strain W22, an environmental strain we isolated from tree hole habitats of mosquito larvae. Plasmids from F. hibernum strain W22 were more efficiently (∼1,250-fold) transferred by electroporation into F. hibernum strain W22 than those isolated from Escherichia coli, thus indicating that an efficient restriction barrier exists between these species. The strong promoter, tac, functional in proteobacteria, did not function in Flavobacterium strains. Therefore, a promoter-trap plasmid, pSCH03, containing a promoterless gfpmut3 gene was constructed. A library of 9,000 clones containing chromosomal fragments of F. hibernum strain W22 in pSCH03 was screened for their ability to drive expression of the promoterless gfpmut3 gene. Twenty strong promoters were used for further study. The transcription start points were determined from seven promoter clones by the 5′ rapid amplification of cDNA ends technique. Promoter consensus sequences from Flavobacterium were identified as TAnnTTTG and TTG, where n is any nucleotide, centered approximately 7 and 33 bp upstream of the transcription start site, respectively. A putative novel ribosome binding site consensus sequence is proposed as TAAAA by aligning the 20-bp regions upstream of the translational start site in 25 genes. Our primary results demonstrate that at least some promoter and ribosome binding site motifs of Flavobacterium strains are unusual within the bacterial domain and suggest an early evolutionary divergence of this bacterial group. The techniques presented here allow for more detailed genetics-based studies and analyses of Flavobacterium species in the environment. PMID:17189449

  15. [Nutrition, acid-base metabolism, cation-anion difference and total base balance in humans].

    PubMed

    Mioni, R; Sala, P; Mioni, G

    2008-01-01

    The relationship between dietary intake and acid-base metabolism has been investigated in the past by means of the inorganic cation-anion difference (C(+)(nm)-A(-)(nm)) method based on dietary ash-acidity titration after the oxidative combustion of food samples. Besides the inorganic components of TA (A(-)(nm)-C(+)(nm)), which are under renal control, there are also metabolizable components (A(-)(nm)-C(+)(nm)) of TA, which are under the control of the intermediate metabolism. The whole body base balance, NBb(W), is obtained only by the application of C(+)(nm)-A(-)(nm) to food, feces and urine, while the metabolizable component (A(-)(nm)-C(+)(nm)) is disregarded. A novel method has been subsequently suggested to calculate the net balance of fixed acid, made up by the difference between the input of net endogenous acid production: NEAP = SO(4)(2-)+A(-)(m)-(C(+)(nm)-A(-)(nm)), and the output of net acid excretion: NAE = TA + NH(4)(+) - HCO(3)(-). This approach has been criticized because 1) it includes metabolizable acids, whose production cannot be measured independently; 2) the specific control of metabolizable acid and base has been incorrectly attributed to the kidney; 3) the inclusion of A-m in the balance input generates an acid overload; 4) the object of measurement in making up a balance has to be the same, a condition not fulfilled as NEAP is different from NAE. Lastly, by rearranging the net balance of the acid equation, the balance of nonmetabolizable acid equation is obtained. Therefore, any discrepancy between these two equations is due to the inaccuracy in the urine measurement of metabolizable cations and/or anions.

  16. Amperometric Low-Potential Detection of Malic Acid Using Single-Wall Carbon Nanotubes Based Electrodes

    PubMed Central

    Arvinte, Adina; Rotariu, Lucian; Bala, Camelia

    2008-01-01

    The electrocatalytical property of single-wall carbon nanotube (SWNT) modified electrode toward NADH detection was explored by cyclic voltammetry and amperometry techniques. The experimental results show that SWNT decrease the overvoltage required for oxidation of NADH (to +300 mV vs. Ag/AgCl) and this property make them suitable for dehydrogenases based biosensors. The behavior of the SWNT modified biosensor for L-malic acid was studied as an example for dehydrogenases biosensor. The amperometric measurements indicate that malate dehydrogenase (MDH) can be strongly adsorbed on the surface of the SWNT-modified electrode to form an approximate monolayer film. Enzyme immobilization in Nafion membrane can increase the biosensor stability. A linear calibration curve was obtained for L-malic acid concentrations between 0.2 and 1mM.

  17. Acid-base chemistry of frustrated water at protein interfaces.

    PubMed

    Fernández, Ariel

    2016-01-01

    Water molecules at a protein interface are often frustrated in hydrogen-bonding opportunities due to subnanoscale confinement. As shown, this condition makes them behave as a general base that may titrate side-chain ammonium and guanidinium cations. Frustration-based chemistry is captured by a quantum mechanical treatment of proton transference and shown to remove same-charge uncompensated anticontacts at the interface found in the crystallographic record and in other spectroscopic information on the aqueous interface. Such observations are untenable within classical arguments, as hydronium is a stronger acid than ammonium or guanidinium. Frustration enables a directed Grotthuss mechanism for proton transference stabilizing same-charge anticontacts.

  18. Acid-base chemistry of frustrated water at protein interfaces.

    PubMed

    Fernández, Ariel

    2016-01-01

    Water molecules at a protein interface are often frustrated in hydrogen-bonding opportunities due to subnanoscale confinement. As shown, this condition makes them behave as a general base that may titrate side-chain ammonium and guanidinium cations. Frustration-based chemistry is captured by a quantum mechanical treatment of proton transference and shown to remove same-charge uncompensated anticontacts at the interface found in the crystallographic record and in other spectroscopic information on the aqueous interface. Such observations are untenable within classical arguments, as hydronium is a stronger acid than ammonium or guanidinium. Frustration enables a directed Grotthuss mechanism for proton transference stabilizing same-charge anticontacts. PMID:26762189

  19. What Is Strong Correlation?

    ERIC Educational Resources Information Center

    Kozak, Marcin

    2009-01-01

    Interpretation of correlation is often based on rules of thumb in which some boundary values are given to help decide whether correlation is non-important, weak, strong or very strong. This article shows that such rules of thumb may do more harm than good, and instead of supporting interpretation of correlation--which is their aim--they teach a…

  20. Classification of pseudo pairs between nucleotide bases and amino acids by analysis of nucleotide-protein complexes.

    PubMed

    Kondo, Jiro; Westhof, Eric

    2011-10-01

    Nucleotide bases are recognized by amino acid residues in a variety of DNA/RNA binding and nucleotide binding proteins. In this study, a total of 446 crystal structures of nucleotide-protein complexes are analyzed manually and pseudo pairs together with single and bifurcated hydrogen bonds observed between bases and amino acids are classified and annotated. Only 5 of the 20 usual amino acid residues, Asn, Gln, Asp, Glu and Arg, are able to orient in a coplanar fashion in order to form pseudo pairs with nucleotide bases through two hydrogen bonds. The peptide backbone can also form pseudo pairs with nucleotide bases and presents a strong bias for binding to the adenine base. The Watson-Crick side of the nucleotide bases is the major interaction edge participating in such pseudo pairs. Pseudo pairs between the Watson-Crick edge of guanine and Asp are frequently observed. The Hoogsteen edge of the purine bases is a good discriminatory element in recognition of nucleotide bases by protein side chains through the pseudo pairing: the Hoogsteen edge of adenine is recognized by various amino acids while the Hoogsteen edge of guanine is only recognized by Arg. The sugar edge is rarely recognized by either the side-chain or peptide backbone of amino acid residues.

  1. Procedure for the quantitative determination of mixtures of nucleic Acid components based on multivariate spectrophotometric Acid-base titrations.

    PubMed

    Saurina, J; Hernández-Cassou, S; Tauler, R; Izquierdo-Ridorsa, A

    1999-01-01

    A new procedure for the quantitative determination of mixtures of nucleic acid components, based on continuous spectrophotometric acid-base titrations and multivariate curve resolution, is proposed. The procedure simultaneously takes into account the spectroscopic and acid-base properties of the compounds, which leads to a higher selectivity. Furthermore, quantitative determination of an analyte in a complex mixture is performed using a synthetic solution as standard containing only the analyte of interest. An intrinsic difficulty in the analysis of spectrometric titration data is the presence of rank deficiency due to closure for the mixtures of two or more compounds. An additional problem can be encountered in some mixtures if species spectra or species concentration profiles are practically identical (rank overlap). However, even in the presence of these rank difficulties, accurate quantitation with prediction errors lower than 5% was obtained. The presence of unknown and uncalibrated interferences in the samples does not affect the quantitative determination of the analyte of interest. The proposed procedure was successfully applied to the analysis of real samples (pharmaceuticals) using synthetic external standards.

  2. Interconversion of CO2 and formic acid by bio-inspired Ir complexes with pendent bases.

    PubMed

    Fujita, Etsuko; Muckerman, James T; Himeda, Yuichiro

    2013-01-01

    Recent investigations of the interconversion of CO2 and formic acid using Ru, Ir and Fe complexes are summarized in this review. During the past several years, both the reaction rates and catalyst stabilities have been significantly improved. Remarkably, the interconversion (i.e., reversibility) has also been achieved under mild conditions in environmentally benign water solvent by slightly changing the pH of the aqueous solution. Only a few catalysts seem to reflect a bio-inspired design such as the use of proton responsive ligands, ligands with pendent bases or acids for a second-coordination-sphere interaction, electroresponsive ligands, and/or ligands having a hydrogen bonding function with a solvent molecule or an added reagent. The most successful of these is an iridium dinuclear complex catalyst that at least has the first three of these characteristics associated with its bridging ligand. By utilizing an acid/base equilibrium for proton removal, the ligand becomes a strong electron donor, resulting in Ir(I) character with a vacant coordination site at each metal center in slightly basic solution. Complemented by DFT calculations, kinetic studies of the rates of formate production using a related family of Ir complexes with and without such functions on the ligand reveal that the rate-determining step for the CO2 hydrogenation is likely to be H2 addition through heterolytic cleavage involving a "proton relay" through the pendent base. The dehydrogenation of formic acid, owing to the proton responsive ligands changing character under slightly acidic pH conditions, is likely to occur by a mechanism with a different rate-determining step. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems. PMID:23174332

  3. Fatty acid-based polyurethane films for wound dressing applications.

    PubMed

    Gultekin, Guncem; Atalay-Oral, Cigdem; Erkal, Sibel; Sahin, Fikret; Karastova, Djursun; Tantekin-Ersolmaz, S Birgul; Guner, F Seniha

    2009-01-01

    Fatty acid-based polyurethane films were prepared for use as potential wound dressing material. The polymerization reaction was carried out with or without catalyst. Polymer films were prepared by casting-evaporation technique with or without crosslink-catalyst. The film prepared from uncatalyzed reaction product with crosslink-catalyst gave slightly higher crosslink density. The mechanical tests showed that, the increase in the tensile strength and decrease in the elongation at break is due to the increase in the degree of crosslinking. All films were flexible, and resisted to acid solution. The films prepared without crosslink-catalyst were more hydrophilic, absorbed more water. The highest permeability values were generally obtained for the films prepared without crosslink catalyst. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films and the polyurethane film prepared from uncatalyzed reaction product without crosslink-catalyst showed better biocompatibility property, closest to the commercial product, Opsite.

  4. Fatty acid-based polyurethane films for wound dressing applications.

    PubMed

    Gultekin, Guncem; Atalay-Oral, Cigdem; Erkal, Sibel; Sahin, Fikret; Karastova, Djursun; Tantekin-Ersolmaz, S Birgul; Guner, F Seniha

    2009-01-01

    Fatty acid-based polyurethane films were prepared for use as potential wound dressing material. The polymerization reaction was carried out with or without catalyst. Polymer films were prepared by casting-evaporation technique with or without crosslink-catalyst. The film prepared from uncatalyzed reaction product with crosslink-catalyst gave slightly higher crosslink density. The mechanical tests showed that, the increase in the tensile strength and decrease in the elongation at break is due to the increase in the degree of crosslinking. All films were flexible, and resisted to acid solution. The films prepared without crosslink-catalyst were more hydrophilic, absorbed more water. The highest permeability values were generally obtained for the films prepared without crosslink catalyst. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films and the polyurethane film prepared from uncatalyzed reaction product without crosslink-catalyst showed better biocompatibility property, closest to the commercial product, Opsite. PMID:18839285

  5. Carboxylic acid free novel isocyanide-based reactions.

    PubMed

    Soeta, Takahiro; Ukaji, Yutaka

    2014-02-01

    In order to develop a practical method for the construction of drug-like and heterocyclic compounds, we have designed a novel Passerini- or Ugi-type reaction system where a compound (which we write in the general form as Z-X) composed of an electrophilic (Z) and a nucleophilic group (X) could essentially perform the same function as the carboxylic acid. Based on this concept, we have developed the O-silylative Passerini reaction and the borinic acid catalyzed α-addition of isocyanides to aldehydes and water. In addition, we have designed and demonstrated the addition reaction of isocyanides to nitrones in the presence of TMSCl to afford the corresponding 1,2,3,4-tetrahydroisoquinoline-1-carboxyamides. Furthermore, a novel [5 + 1] cycloaddition of isocyanide was explored with C,N-cyclic N'-acyl azomethine imines as a "1,5-dipole" via a strategy involving intramolecular trapping of the isocyanide.

  6. Nucleic acid-based tissue biomarkers of urologic malignancies.

    PubMed

    Dietrich, Dimo; Meller, Sebastian; Uhl, Barbara; Ralla, Bernhard; Stephan, Carsten; Jung, Klaus; Ellinger, Jörg; Kristiansen, Glen

    2014-08-01

    Molecular biomarkers play an important role in the clinical management of cancer patients. Biomarkers allow estimation of the risk of developing cancer; help to diagnose a tumor, ideally at an early stage when cure is still possible; and aid in monitoring disease progression. Furthermore, they hold the potential to predict the outcome of the disease (prognostic biomarkers) and the response to therapy (predictive biomarkers). Altogether, biomarkers will help to avoid tumor-related deaths and reduce overtreatment, and will contribute to increased survival and quality of life in cancer patients due to personalized treatments. It is well established that the process of carcinogenesis is a complex interplay between genomic predisposition, acquired somatic mutations, epigenetic changes and genomic aberrations. Within this complex interplay, nucleic acids, i.e. RNA and DNA, play a fundamental role and therefore represent ideal candidates for biomarkers. They are particularly promising candidates because sequence-specific hybridization and amplification technologies allow highly accurate and sensitive assessment of these biomarker levels over a broad dynamic range. This article provides an overview of nucleic acid-based biomarkers in tissues for the management of urologic malignancies, i.e. tumors of the prostate, testis, kidney, penis, urinary bladder, renal pelvis, ureter and other urinary organs. Special emphasis is put on genomic, transcriptomic and epigenomic biomarkers (SNPs, mutations [genomic and mitochondrial], microsatellite instabilities, viral and bacterial DNA, DNA methylation and hydroxymethylation, mRNA expression, and non-coding RNAs [lncRNA, miRNA, siRNA, piRNA, snRNA, snoRNA]). Due to the multitude of published biomarker candidates, special focus is given to the general applicability of different molecular classes as biomarkers and some particularly promising nucleic acid biomarkers. Furthermore, specific challenges regarding the development and clinical

  7. Bio-based production of organic acids with Corynebacterium glutamicum

    PubMed Central

    Wieschalka, Stefan; Blombach, Bastian; Bott, Michael; Eikmanns, Bernhard J

    2013-01-01

    The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, l-and d-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers. Funding Information Work in the laboratories of the authors was supported by the Fachagentur Nachwachsende Rohstoffe (FNR) of the Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV; FNR Grants 220-095-08A and 220-095-08D; Bio-ProChemBB project, ERA-IB programme), by the Deutsche Bundesstiftung Umwelt (DBU Grant AZ13040/05) and the Evonik Degussa AG. PMID

  8. DEOXYRIBONUCLEIC ACID BASE COMPOSITION OF PROTEUS AND PROVIDENCE ORGANISMS

    PubMed Central

    Falkow, Stanley; Ryman, I. R.; Washington, O.

    1962-01-01

    Falkow, Stanley (Walter Reed Army Institute of Research, Washington D.C.), I. R. Ryman, and O. Washington. Deoxyribonucleic acid base composition of Proteus and Providence organisms. J. Bacteriol. 83:1318–1321. 1962.—Deoxyribonucleic acids (DNA) from various species of Proteus and of Providence bacteria have been examined for their guanine + cytosine (GC) content. P. vulgaris, P. mirabilis, and P. rettgeri possess essentially identical mean GC contents of 39%, and Providence DNA has a GC content of 41.5%. In marked contrast, P. morganii DNA was found to contain 50% GC. The base composition of P. morganii is only slightly lower than those observed for representatives of the Escherichia, Shigella, and Salmonella groups. Aerobacter and Serratia differ significantly from the other members of the family by their relatively high GC content. Since a minimal requirement for genetic compatibility among different species appears to be similarity of their DNA base composition, it is suggested that P. morganii is distinct genetically from the other species of Proteus as well as Providence strains. The determination of the DNA base composition of microorganisms is important for its predictive information. This information should prove of considerable value in investigating genetic and taxonomic relationships among bacteria. PMID:13891463

  9. Tank-Treading of Erythrocytes in Strong Shear Flows via a Nonstiff Cytoskeleton-Based Continuum Computational Modeling

    PubMed Central

    Dodson, W.R.; Dimitrakopoulos, P.

    2010-01-01

    We develop a computationally efficient cytoskeleton-based continuum erythrocyte algorithm. The cytoskeleton is modeled as a two-dimensional elastic solid with comparable shearing and area-dilatation resistance that follows a material law (Skalak, R., A. Tozeren, R. P. Zarda, and S. Chien. 1973. Strain energy function of red blood cell membranes. Biophys. J. 13:245–264). Our modeling enforces the global area-incompressibility of the spectrin skeleton (being enclosed beneath the lipid bilayer in the erythrocyte membrane) via a nonstiff, and thus efficient, adaptive prestress procedure which accounts for the (locally) isotropic stress imposed by the lipid bilayer on the cytoskeleton. In addition, we investigate the dynamics of healthy human erythrocytes in strong shear flows with capillary number Ca = O(1) and small-to-moderate viscosity ratios 0.001 ≤ λ ≤ 1.5. These conditions correspond to a wide range of surrounding medium viscosities (4–600 mPa s) and shear flow rates (0.02–440 s−1), and match those used in ektacytometry systems. Our computational results on the cell deformability and tank-treading frequency are compared with ektacytometry findings. The tank-treading period is shown to be inversely proportional to the shear rate and to increase linearly with the ratio of the cytoplasm viscosity to that of the suspending medium. Our modeling also predicts that the cytoskeleton undergoes measurable local area dilatation and compression during the tank-treading of the cells. PMID:21044588

  10. Superabsorbent biphasic system based on poly(lactic acid) and poly(acrylic acid)

    NASA Astrophysics Data System (ADS)

    Sartore, Luciana; Pandini, Stefano; Baldi, Francesco; Bignotti, Fabio

    2016-05-01

    In this research work, biocomposites based on crosslinked particles of poly(acrylic acid), commonly used as superabsorbent polymer (SAP), and poly-L-lactic acid (PLLA) were developed to elucidate the role of the filler (i.e., polymeric crosslinked particles) on the overall physico-mechanical behavior and to obtain superabsorbent thermoplastic products. Samples prepared by melt-blending of components in different ratios showed a biphasic system with a regular distribution of particles, with diameter ranging from 5 to 10 μm, within the PLLA polymeric matrix. The polymeric biphasic system, coded PLASA i.e. superabsorbent poly(lactic acid), showed excellent swelling properties, demonstrating that cross-linked particles retain their superabsorbent ability, as in their free counterparts, even if distributed in a thermoplastic polymeric matrix. The thermal characteristics of the biocomposites evidence enhanced thermal stability in comparison with neat PLLA and also mechanical properties are markedly modified by addition of crosslinked particles which induce regular stiffening effect. Furthermore, in aqueous environments the particles swell and are leached from PLLA matrix generating very high porosity. These new open-pore PLLA foams, produced in absence of organic solvents and chemical foaming agents, with good physico-mechanical properties appear very promising for several applications, for instance in tissue engineering for scaffold production.

  11. General analytical procedure for determination of acidity parameters of weak acids and bases.

    PubMed

    Pilarski, Bogusław; Kaliszan, Roman; Wyrzykowski, Dariusz; Młodzianowski, Janusz; Balińska, Agata

    2015-01-01

    The paper presents a new convenient, inexpensive, and reagent-saving general methodology for the determination of pK a values for components of the mixture of diverse chemical classes weak organic acids and bases in water solution, without the need to separate individual analytes. The data obtained from simple pH-metric microtitrations are numerically processed into reliable pK a values for each component of the mixture. Excellent agreement has been obtained between the determined pK a values and the reference literature data for compounds studied.

  12. Functional nucleic-acid-based sensors for environmental monitoring.

    PubMed

    Sett, Arghya; Das, Suradip; Bora, Utpal

    2014-10-01

    Efforts to replace conventional chromatographic methods for environmental monitoring with cheaper and easy to use biosensors for precise detection and estimation of hazardous environmental toxicants, water or air borne pathogens as well as various other chemicals and biologics are gaining momentum. Out of the various types of biosensors classified according to their bio-recognition principle, nucleic-acid-based sensors have shown high potential in terms of cost, sensitivity, and specificity. The discovery of catalytic activities of RNA (ribozymes) and DNA (DNAzymes) which could be triggered by divalent metallic ions paved the way for their extensive use in detection of heavy metal contaminants in environment. This was followed with the invention of small oligonucleotide sequences called aptamers which can fold into specific 3D conformation under suitable conditions after binding to target molecules. Due to their high affinity, specificity, reusability, stability, and non-immunogenicity to vast array of targets like small and macromolecules from organic, inorganic, and biological origin, they can often be exploited as sensors in industrial waste management, pollution control, and environmental toxicology. Further, rational combination of the catalytic activity of DNAzymes and RNAzymes along with the sequence-specific binding ability of aptamers have given rise to the most advanced form of functional nucleic-acid-based sensors called aptazymes. Functional nucleic-acid-based sensors (FNASs) can be conjugated with fluorescent molecules, metallic nanoparticles, or quantum dots to aid in rapid detection of a variety of target molecules by target-induced structure switch (TISS) mode. Although intensive research is being carried out for further improvements of FNAs as sensors, challenges remain in integrating such bio-recognition element with advanced transduction platform to enable its use as a networked analytical system for tailor made analysis of environmental

  13. Liquid crystal based biosensors for bile acid detection

    NASA Astrophysics Data System (ADS)

    He, Sihui; Liang, Wenlang; Tanner, Colleen; Fang, Jiyu; Wu, Shin-Tson

    2013-03-01

    The concentration level of bile acids is a useful indicator for early diagnosis of liver diseases. The prevalent measurement method in detecting bile acids is the chromatography coupled with mass spectrometry, which is precise yet expensive. Here we present a biosensor platform based on liquid crystal (LC) films for the detection of cholic acid (CA). This platform has the advantage of low cost, label-free, solution phase detection and simple analysis. In this platform, LC film of 4-Cyano-4'-pentylbiphenyl (5CB) was hosted by a copper grid supported with a polyimide-coated glass substrate. By immersing into sodium dodecyl sulfate (SDS) solution, the LC film was coated with SDS which induced a homeotropic anchoring of 5CB. Addition of CA introduced competitive adsorption between CA and SDS at the interface, triggering a transition from homeotropic to homogeneous anchoring. The detection limit can be tuned by changing the pH value of the solution from 12uM to 170uM.

  14. Paediatric acid-base disorders: A case-based review of procedures and pitfalls.

    PubMed

    Carmody, J Bryan; Norwood, Victoria F

    2013-01-01

    Acid-base disorders occur frequently in paediatric patients. Despite the perception that their analysis is complex and difficult, a straightforward set of rules is sufficient to interpret even the most complex disorders - provided certain pitfalls are avoided. Using a case-based approach, the present article reviews the fundamental concepts of acid-base analysis and highlights common mistakes and oversights. Specific topics include the proper identification of the primary disorder; distinguishing compensatory changes from additional primary disorders; use of the albumin-corrected anion gap to generate a differential diagnosis for patients with metabolic acidosis; screening for mixed disorders with the delta-delta formula; recognizing the limits of compensation; use of the anion gap to identify 'hidden' acidosis; and the importance of using information from the history and physical examination to identify the specific cause of a patient's acid-base disturbance.

  15. The comprehensive acid-base characterization of glutathione

    NASA Astrophysics Data System (ADS)

    Mirzahosseini, Arash; Somlyay, Máté; Noszál, Béla

    2015-02-01

    Glutathione in its thiol (GSH) and disulfide (GSSG) forms, and 4 related compounds were studied by 1H NMR-pH titrations and a case-tailored evaluation method. The resulting acid-base properties are quantified in terms of 128 microscopic protonation constants; the first complete set of such parameters for this vitally important pair of compounds. The concomitant 12 interactivity parameters were also determined. Since biological redox systems are regularly compared to the GSH-GSSG pair, the eight microscopic thiolate basicities determined this way are exclusive means for assessing subtle redox parameters in a wide pH range.

  16. Conducting Polymer Based Nucleic Acid Sensor for Environment Monitoring

    NASA Astrophysics Data System (ADS)

    Malhotra, Bansi Dhar; Prabhakar, Nirmal; Solanki, Pratima R.

    Nucleic acid sensor based on polyaniline has been fabricated by covalently immobilizing double stranded calf thymus (dsCT) DNA onto perchlorate (ClO-4) doped polyaniline (PANI) film deposited onto indium-tin-oxide (ITO) glass plate using 1-(3-(dimethylamino) propyl)-3-ethylcarbodiimide hydrochloride (EDC)/N-hydroxyl succinimide (NHS) chemistry. These dsCT-DNA-PANI/ITO and PANI/ITO electrodes have been characterized using square wave voltammetry, electrochemical impedance, and Fourier-transform-infra-red (FTIR) measurements. This disposable dsCT-DNA-PANI/ITO bioelectrode is stable for about four months, can be used to detect arsenic trioxide (0.1ppm) in 30s.

  17. Gallic acid-based indanone derivatives as anticancer agents.

    PubMed

    Saxena, Hari Om; Faridi, Uzma; Srivastava, Suchita; Kumar, J K; Darokar, M P; Luqman, Suaib; Chanotiya, C S; Krishna, Vinay; Negi, Arvind S; Khanuja, S P S

    2008-07-15

    Gallic acid-based indanone derivatives have been synthesised. Some of the indanones showed very good anticancer activity in MTT assay. Compounds 10, 11, 12 and 14 possessed potent anticancer activity against various human cancer cell lines. The most potent indanone (10, IC(50)=2.2 microM), against MCF-7, that is, hormone-dependent breast cancer cell line, showed no toxicity to human erythrocytes even at higher concentrations (100 microg/ml, 258 microM). While, indanones 11, 12 and 14 showed toxicities to erythrocytes at higher concentrations.

  18. Acid-Base Homeostasis: Overview for Infusion Nurses.

    PubMed

    Masco, Natalie A

    2016-01-01

    Acid-base homeostasis is essential to normal function of the human body. Even slight alterations can significantly alter physiologic processes at the tissue and cellular levels. To optimally care for patients, nurses must be able to recognize signs and symptoms that indicate deviations from normal. Nurses who provide infusions to patients-whether in acute care, home care, or infusion center settings-have a responsibility to be able to recognize the laboratory value changes that occur with the imbalance and appreciate the treatment options, including intravenous infusions. PMID:27598068

  19. A fully automatic system for acid-base coulometric titrations.

    PubMed

    Cladera, A; Caro, A; Estela, J M; Cerdà, V

    1990-01-01

    An automatic system for acid-base titrations by electrogeneration of H(+) and OH(-) ions, with potentiometric end-point detection, was developed. The system includes a PC-compatible computer for instrumental control, data acquisition and processing, which allows up to 13 samples to be analysed sequentially with no human intervention.The system performance was tested on the titration of standard solutions, which it carried out with low errors and RSD. It was subsequently applied to the analysis of various samples of environmental and nutritional interest, specifically waters, soft drinks and wines.

  20. [Acid-base equilibrium in sportsmen during physical exercise].

    PubMed

    Brinzak, V P; Kalinskiĭ, M I; Val'tin, A I; Povzhitkova, M S

    1983-01-01

    Acid-base balance in venous blood of basketball players was studied under specific loadings of various intensity by means of the micro-Astrup device. It is established that under acyclic loadings (throwing the ball into the basket) the state of metabolic acidosis is developed in the sportsmen and the more intensive the work, the higher the degree of the state of metabolic acidosis. The efficiency of actions of the persons examined was in inverse dependence on the degree of metabolic disturbances, i.e. the least efficiency was marked under the most profound acidosis.

  1. A one-step colorimetric acid-base titration sensor using a complementary color changing coordination system.

    PubMed

    Cho, Hui Hun; Kim, Si Hyun; Heo, Jun Hyuk; Moon, Young Eel; Choi, Young Hun; Lim, Dong Cheol; Han, Kwon-Hoon; Lee, Jung Heon

    2016-06-21

    We report the development of a colorimetric sensor that allows for the quantitative measurement of the acid content via acid-base titration in a single-step. In order to create the sensor, we used a cobalt coordination system (Co-complex sensor) that changes from greenish blue colored Co(H2O)4(OH)2 to pink colored Co(H2O)6(2+) after neutralization. Greenish blue and pink are two complementary colors with a strong contrast. As a certain amount of acid is introduced to the Co-complex sensor, a portion of greenish blue colored Co(H2O)4(OH)2 changes to pink colored Co(H2O)6(2+), producing a different color. As the ratio of greenish blue and pink in the Co-complex sensor is determined by the amount of neutralization reaction occurring between Co(H2O)4(OH)2 and an acid, the sensor produced a spectrum of green, yellow green, brown, orange, and pink colors depending on the acid content. In contrast, the color change appeared only beyond the end point for normal acid-base titration. When we mixed this Co-complex sensor with different concentrations of citric acid, tartaric acid, and malic acid, three representative organic acids in fruits, we observed distinct color changes for each sample. This color change could also be observed in real fruit juice. When we treated the Co-complex sensor with real tangerine juice, it generated diverse colors depending on the concentration of citric acid in each sample. These results provide a new angle on simple but quantitative measurements of analytes for on-site usage in various applications, such as in food, farms, and the drug industry. PMID:27143645

  2. A one-step colorimetric acid-base titration sensor using a complementary color changing coordination system.

    PubMed

    Cho, Hui Hun; Kim, Si Hyun; Heo, Jun Hyuk; Moon, Young Eel; Choi, Young Hun; Lim, Dong Cheol; Han, Kwon-Hoon; Lee, Jung Heon

    2016-06-21

    We report the development of a colorimetric sensor that allows for the quantitative measurement of the acid content via acid-base titration in a single-step. In order to create the sensor, we used a cobalt coordination system (Co-complex sensor) that changes from greenish blue colored Co(H2O)4(OH)2 to pink colored Co(H2O)6(2+) after neutralization. Greenish blue and pink are two complementary colors with a strong contrast. As a certain amount of acid is introduced to the Co-complex sensor, a portion of greenish blue colored Co(H2O)4(OH)2 changes to pink colored Co(H2O)6(2+), producing a different color. As the ratio of greenish blue and pink in the Co-complex sensor is determined by the amount of neutralization reaction occurring between Co(H2O)4(OH)2 and an acid, the sensor produced a spectrum of green, yellow green, brown, orange, and pink colors depending on the acid content. In contrast, the color change appeared only beyond the end point for normal acid-base titration. When we mixed this Co-complex sensor with different concentrations of citric acid, tartaric acid, and malic acid, three representative organic acids in fruits, we observed distinct color changes for each sample. This color change could also be observed in real fruit juice. When we treated the Co-complex sensor with real tangerine juice, it generated diverse colors depending on the concentration of citric acid in each sample. These results provide a new angle on simple but quantitative measurements of analytes for on-site usage in various applications, such as in food, farms, and the drug industry.

  3. The Mechanism of MIO-Based Aminomutases in beta-Amino Acid Biosynthesis

    SciTech Connect

    Christianson,C.; Montavon, T.; Festin, G.; Cooke, H.; Shen, B.; Bruner, S.

    2007-01-01

    {beta}-Amino acids are widely used building blocks in both natural and synthetic compounds. Aromatic {beta}-amino acids can be biosynthesized directly from proteinogenic a-amino acids by the action of MIO (4-methylideneimidazole-5-one)-based aminomutase enzymes. The uncommon cofactor MIO plays a role in both ammonia lyases and 2, 3-aminomutases; however, the precise mechanism of the cofactor has not been resolved. Here we provide evidence that the electrophilic cofactor uses covalent catalysis through the substrate amine to direct the elimination and subsequent readdition of ammonia. A mechanism-based inhibitor was synthesized and the X-ray cocomplex structure was determined to 2.0 Angstroms resolution. The inhibitor halts the chemistry of the reverse reaction, providing a stable complex that establishes the mode of substrate binding and the importance of tyrosine 63 in the chemistry. The proposed mechanism is consistent with the biochemistry of aminomutases and ammonia lyases and provides strong support for an amine-adduct mechanism of catalysis for this enzyme class.

  4. 78 FR 36698 - Microbiology Devices; Reclassification of Nucleic Acid-Based Systems for Mycobacterium tuberculosis

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-19

    ... Nucleic Acid-Based Systems for Mycobacterium tuberculosis Complex in Respiratory Specimens AGENCY: Food...) is proposing to reclassify nucleic acid-based in vitro diagnostic devices for the detection of... Controls Guideline: Nucleic Acid-Based In Vitro Diagnostic Devices for the Detection of...

  5. Development of a highly sensitive MIP based-QCM nanosensor for selective determination of cholic acid level in body fluids.

    PubMed

    Gültekin, Aytaç; Karanfil, Gamze; Sönmezoğlu, Savaş; Say, Rıdvan

    2014-09-01

    Determination of cholic acid is very important and necessary in body fluids due to its both pharmaceutical and clinical significance. In this study, a quartz crystal microbalance (QCM) nanosensor, which is imprinted cholic acid, has been developed for the assignation of cholic acid. The cholic acid selective memories have been generated on QCM electrode surface by using molecularly imprinted polymer (MIP) based on methacryloylamidohistidine-copper (II) (MAH-Cu(II)) pre-organized monomer. The cholic acid imprinted nanosensor was characterized by atomic force microscopy (AFM) and then analytical performance of the cholic acid imprinted QCM nanosensor was studied. The detection limit was found to be 0.0065μM with linear range of 0.01-1,000 μM. Moreover, the high value of Langmuir constant (b) (7.3*10(5)) obtained by Langmuir graph showed that the cholic acid imprinted nanosensor had quite strong binding sites affinity. At the last step of this procedure, cholic acid levels in body fluids were determined by the prepared imprinted QCM nanosensor.

  6. Increments to chiral recognition facilitating enantiomer separations of chiral acids, bases, and ampholytes using Cinchona-based zwitterion exchanger chiral stationary phases.

    PubMed

    Wernisch, Stefanie; Pell, Reinhard; Lindner, Wolfgang

    2012-07-01

    The intramolecular distances of anion and cation exchanger sites of zwitterionic chiral stationary phases represent potential tuning sites for enantiomer selectivity. In this contribution, we investigate the influence of alkanesulfonic acid chain length and flexibility on enantiomer separations of chiral acids, bases, and amphoteric molecules for six Cinchona alkaloid-based chiral stationary phases in comparison with structurally related anion and cation exchangers. Employing polar-organic elution conditions, we observed an intramolecular counterion effect for acidic analytes which led to reduced retention times but did not impair enantiomer selectivities. Retention of amphoteric analytes is based on simultaneous double ion pairing of their charged functional groups with the acidic and basic sites of the zwitterionic selectors. A chiral center in the vicinity of the strong cation exchanger site is vital for chiral separations of bases. Sterically demanding side chains are beneficial for separations of free amino acids. Enantioseparations of free (un-derivatized) peptides were particularly successful in stationary phases with straight-chain alkanesulfonic acid sites, pointing to a beneficial influence of more flexible moieties. In addition, we observed pseudo-enantiomeric behavior of quinine and quinidine-derived chiral stationary phases facilitating reversal of elution orders for all analytes.

  7. Effect of temperature on the acid-base properties of the alumina surface: microcalorimetry and acid-base titration experiments.

    PubMed

    Morel, Jean-Pierre; Marmier, Nicolas; Hurel, Charlotte; Morel-Desrosiers, Nicole

    2006-06-15

    Sorption reactions on natural or synthetic materials that can attenuate the migration of pollutants in the geosphere could be affected by temperature variations. Nevertheless, most of the theoretical models describing sorption reactions are at 25 degrees C. To check these models at different temperatures, experimental data such as the enthalpies of sorption are thus required. Highly sensitive microcalorimeters can now be used to determine the heat effects accompanying the sorption of radionuclides on oxide-water interfaces, but enthalpies of sorption cannot be extracted from microcalorimetric data without a clear knowledge of the thermodynamics of protonation and deprotonation of the oxide surface. However, the values reported in the literature show large discrepancies and one must conclude that, amazingly, this fundamental problem of proton binding is not yet resolved. We have thus undertaken to measure by titration microcalorimetry the heat effects accompanying proton exchange at the alumina-water interface at 25 degrees C. Based on (i) the surface sites speciation provided by a surface complexation model (built from acid-base titrations at 25 degrees C) and (ii) results of the microcalorimetric experiments, calculations have been made to extract the enthalpic variations associated respectively to first and second deprotonation of the alumina surface. Values obtained are deltaH1 = 80+/-10 kJ mol(-1) and deltaH2 = 5+/-3 kJ mol(-1). In a second step, these enthalpy values were used to calculate the alumina surface acidity constants at 50 degrees C via the van't Hoff equation. Then a theoretical titration curve at 50 degrees C was calculated and compared to the experimental alumina surface titration curve. Good agreement between the predicted acid-base titration curve and the experimental one was observed.

  8. Design of chitosan-based nanoparticles functionalized with gallic acid.

    PubMed

    Lamarra, J; Rivero, S; Pinotti, A

    2016-10-01

    Active nanoparticles based on chitosan could be applied as a support for the modulation of gallic acid delivery. In this sense, these nanostructures could be employed in different fields such as food, packaging, and pharmaceutical areas. The design parameters of chitosan-based nanoparticles functionalized with gallic acid (GA) were optimized through RSM by means of the analysis of zeta potential (ZP) and percentage encapsulation efficiency (PEE). The nanoparticles were prepared by ionotropic gelation using tripolyphosphate (TPP), at different combinations of chitosan (CH) concentration, CH:TPP ratio and GA. Global desirability methodology allowed finding the optimum formulation that included CH 0.76% (w/w), CH:TPP ratio of 5 and 37mgGA/gCH leading to ZP of +50mV and 82% of PEE. Analysis through QuickScan and turbidity demonstrated that the most stable nanoparticle suspensions were achieved combining concentrations of chitosan ranging between 0.5 and 0.75% with CH:TPP ratios higher than 3. These suspensions had high stability confirmed by means ZP and transmittance values which were higher than +25mV and 0.21 on average, respectively, as well as nanoparticle diameters of about 140nm. FTIR revealed the occurrence of both hydrogen bond and ionic interactions of CH-TPP which allowed the encapsulation and the improvement of the stability of the active agent. PMID:27287172

  9. Sphingoid bases inhibit acid-induced demineralization of hydroxyapatite.

    PubMed

    Valentijn-Benz, Marianne; van 't Hof, Wim; Bikker, Floris J; Nazmi, Kamran; Brand, Henk S; Sotres, Javier; Lindh, Liselott; Arnebrant, Thomas; Veerman, Enno C I

    2015-01-01

    Calcium hydroxyapatite (HAp), the main constituent of dental enamel, is inherently susceptible to the etching and dissolving action of acids, resulting in tooth decay such as dental caries and dental erosion. Since the prevalence of erosive wear is gradually increasing, there is urgent need for agents that protect the enamel against erosive attacks. In the present study we studied in vitro the anti-erosive effects of a number of sphingolipids and sphingoid bases, which form the backbone of sphingolipids. Pretreatment of HAp discs with sphingosine, phytosphingosine (PHS), PHS phosphate and sphinganine significantly protected these against acid-induced demineralization by 80 ± 17%, 78 ± 17%, 78 ± 7% and 81 ± 8%, respectively (p < 0.001). On the other hand, sphingomyelin, acetyl PHS, octanoyl PHS and stearoyl PHS had no anti-erosive effects. Atomic force measurement revealed that HAp discs treated with PHS were almost completely and homogeneously covered by patches of PHS. This suggests that PHS and other sphingoid bases form layers on the surface of HAp, which act as diffusion barriers against H(+) ions. In principle, these anti-erosive properties make PHS and related sphingosines promising and attractive candidates as ingredients in oral care products.

  10. Applications of synchrotron-based spectroscopic techniques in studying nucleic acids and nucleic acid-functionalized nanomaterials.

    PubMed

    Wu, Peiwen; Yu, Yang; McGhee, Claire E; Tan, Li Huey; Lu, Yi

    2014-12-10

    In this review, we summarize recent progress in the application of synchrotron-based spectroscopic techniques for nucleic acid research that takes advantage of high-flux and high-brilliance electromagnetic radiation from synchrotron sources. The first section of the review focuses on the characterization of the structure and folding processes of nucleic acids using different types of synchrotron-based spectroscopies, such as X-ray absorption spectroscopy, X-ray emission spectroscopy, X-ray photoelectron spectroscopy, synchrotron radiation circular dichroism, X-ray footprinting and small-angle X-ray scattering. In the second section, the characterization of nucleic acid-based nanostructures, nucleic acid-functionalized nanomaterials and nucleic acid-lipid interactions using these spectroscopic techniques is summarized. Insights gained from these studies are described and future directions of this field are also discussed.

  11. Applications of synchrotron-based spectroscopic techniques in studying nucleic acids and nucleic acid-functionalized nanomaterials

    PubMed Central

    Wu, Peiwen; Yu, Yang; McGhee, Claire E.; Tan, Li Huey

    2014-01-01

    In this review, we summarize recent progresses in the application of synchrotron-based spectroscopic techniques for nucleic acid research that takes advantage of high-flux and high-brilliance electromagnetic radiation from synchrotron sources. The first section of the review focuses on the characterization of the structure and folding processes of nucleic acids using different types of synchrotron-based spectroscopies, such as X-ray absorption spectroscopy, X-ray emission spectroscopy, X-ray photoelectron spectroscopy, synchrotron radiation circular dichroism, X-ray footprinting and small-angle X-ray scattering. In the second section, the characterization of nucleic acid-based nanostructures, nucleic acid-functionalized nanomaterials and nucleic acid-lipid interactions using these spectroscopic techniques is summarized. Insights gained from these studies are described and future directions of this field are also discussed. PMID:25205057

  12. Effects of intravenous solutions on acid-base equilibrium: from crystalloids to colloids and blood components.

    PubMed

    Langer, Thomas; Ferrari, Michele; Zazzeron, Luca; Gattinoni, Luciano; Caironi, Pietro

    2014-01-01

    Intravenous fluid administration is a medical intervention performed worldwide on a daily basis. Nevertheless, only a few physicians are aware of the characteristics of intravenous fluids and their possible effects on plasma acid-base equilibrium. According to Stewart's theory, pH is independently regulated by three variables: partial pressure of carbon dioxide, strong ion difference (SID), and total amount of weak acids (ATOT). When fluids are infused, plasma SID and ATOT tend toward the SID and ATOT of the administered fluid. Depending on their composition, fluids can therefore lower, increase, or leave pH unchanged. As a general rule, crystalloids having a SID greater than plasma bicarbonate concentration (HCO₃-) cause an increase in plasma pH (alkalosis), those having a SID lower than HCO₃- cause a decrease in plasma pH (acidosis), while crystalloids with a SID equal to HCO₃- leave pH unchanged, regardless of the extent of the dilution. Colloids and blood components are composed of a crystalloid solution as solvent, and the abovementioned rules partially hold true also for these fluids. The scenario is however complicated by the possible presence of weak anions (albumin, phosphates and gelatins) and their effect on plasma pH. The present manuscript summarises the characteristics of crystalloids, colloids, buffer solutions and blood components and reviews their effect on acid-base equilibrium. Understanding the composition of intravenous fluids, along with the application of simple physicochemical rules best described by Stewart's approach, are pivotal steps to fully elucidate and predict alterations of plasma acid-base equilibrium induced by fluid therapy.

  13. A comprehensive classification of nucleic acid structural families based on strand direction and base pairing.

    PubMed Central

    Lavery, R; Zakrzewska, K; Sun, J S; Harvey, S C

    1992-01-01

    We propose a classification of DNA structures formed from 1 to 4 strands, based only on relative strand directions, base to strand orientation and base pairing geometries. This classification and its associated notation enable all nucleic acids to be grouped into structural families and bring to light possible structures which have not yet been observed experimentally. It also helps in understanding transitions between families and can assist in the design of multistrand structures. PMID:1383936

  14. Modeling the acid-base surface chemistry of montmorillonite.

    PubMed

    Bourg, Ian C; Sposito, Garrison; Bourg, Alain C M

    2007-08-15

    Proton uptake on montmorillonite edge surfaces can control pore water pH, solute adsorption, dissolution kinetics and clay colloid behavior in engineered clay barriers and natural weathering environments. Knowledge of proton uptake reactions, however, is currently limited by strong discrepancies between reported montmorillonite titration data sets and by conflicting estimates of edge structure, reactivity and electrostatics. In the present study, we show that the apparent discrepancy between titration data sets results in large part from the widespread use of an erroneous assumption of zero specific net proton surface charge at the onset of titration. Using a novel simulation scheme involving a surface chemistry model to simulate both pretreatment and titration, we find that montmorillonite edge surface chemistry models that account for the "spillover" of electrostatic potential from basal onto edge surfaces and for the stabilization of deprotonated Al-Si bridging sites through bond-length relaxation at the edge surface can reproduce key features of the best available experimental titration data (the influence of pretreatment conditions on experimental results, the absence of a point of zero salt effect, buffer capacity in the acidic pH range). However, no combination of current models of edge surface structure, reactivity and electrostatics can quantitatively predict, without fitted parameters, the experimental titration data over the entire range of pH (4.5 to 9) and ionic strength (0.001 to 0.5 mol dm(-3)) covered by available data.

  15. Acid-base balance in ducks (Anas platyrhynchos) during involuntary submergence.

    PubMed

    Shimizu, M; Jones, D R

    1987-02-01

    Measurements of all the major independent variables [arterial CO2 tension (PaCO2); strong-ion difference ([SID]), and total protein content, which approximate total weak acid concentration in plasma] are essential for understanding changes in acid-base balance in plasma. During involuntary submergence of 1, 2, or 4 min, PaCO2 in ducks increased and arterial pH (pHa) decreased. During 1-min dives there were no significant changes in any strong ions. In both 2- and 4-min dives, there was a significant increase in [lactate-], but because of an increase in equal magnitude of [Na+], [SID] did not change. During recovery from all dives the plasma remained acidotic for several minutes, although PaCO2 fell below predive levels in less than 1 min. [Lactate-] increased in the recovery period. There were no changes in total protein content during submergence or recovery. Breathing 100% O2 before 2-min dives caused a reduction in [lactate-] production and release during and after the dive, although due to a marked increased in PaCO2, pHa fell as low as in 4-min dives after breathing air. After 1 min of recovery, pHa returned to normal along with the restoration of the predive level of PaCO2. We conclude that the acidosis during involuntary submergence is due solely to an increase in PaCO2, whereas in recovery it is caused by decreased [SID]. PMID:3101522

  16. Probe kit for identifying a base in a nucleic acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    2001-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  17. Hybridization and sequencing of nucleic acids using base pair mismatches

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    2001-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  18. Method of Identifying a Base in a Nucleic Acid

    DOEpatents

    Fodor, Stephen P. A.; Lipshutz, Robert J.; Huang, Xiaohua

    1999-01-01

    Devices and techniques for hybridization of nucleic acids and for determining the sequence of nucleic acids. Arrays of nucleic acids are formed by techniques, preferably high resolution, light-directed techniques. Positions of hybridization of a target nucleic acid are determined by, e.g., epifluorescence microscopy. Devices and techniques are proposed to determine the sequence of a target nucleic acid more efficiently and more quickly through such synthesis and detection techniques.

  19. Gallic acid indanone and mangiferin xanthone are strong determinants of immunosuppressive anti-tumour effects of Mangifera indica L. bark in MDA-MB231 breast cancer cells.

    PubMed

    García-Rivera, Dagmar; Delgado, René; Bougarne, Nadia; Haegeman, Guy; Berghe, Wim Vanden

    2011-06-01

    Vimang is a standardized extract derived from Mango bark (Mangifera Indica L.), commonly used as anti-inflammatory phytomedicine, which has recently been used to complement cancer therapies in cancer patients. We have further investigated potential anti-tumour effects of glucosylxanthone mangiferin and indanone gallic acid, which are both present in Vimang extract. We observed significant anti-tumour effects of both Vimang constituents in the highly aggressive and metastatic breast cancer cell type MDA-MB231. At the molecular level, mangiferin and gallic acid both inhibit classical NFκB activation by IKKα/β kinases, which results in impaired IκB degradation, NFκB translocation and NFκB/DNA binding. In contrast to the xanthone mangiferin, gallic acid further inhibits additional NFκB pathways involved in cancer cell survival and therapy resistance, such as MEK1, JNK1/2, MSK1, and p90RSK. This results in combinatorial inhibition of NFκB activity by gallic acid, which results in potent inhibition of NFκB target genes involved in inflammation, metastasis, anti-apoptosis and angiogenesis, such as IL-6, IL-8, COX2, CXCR4, XIAP, bcl2, VEGF. The cumulative NFκB inhibition by gallic acid, but not mangiferin, is also reflected at the level of cell survival, which reveals significant tumour cytotoxic effects in MDA-MB231 cells. Altogether, we identify gallic acid, besides mangiferin, as an essential anti-cancer component in Vimang extract, which demonstrates multifocal inhibition of NFκB activity in the cancer-inflammation network.

  20. Acid-base titrations using microfluidic paper-based analytical devices.

    PubMed

    Karita, Shingo; Kaneta, Takashi

    2014-12-16

    Rapid and simple acid-base titration was accomplished using a novel microfluidic paper-based analytical device (μPAD). The μPAD was fabricated by wax printing and consisted of ten reservoirs for reaction and detection. The reaction reservoirs contained various amounts of a primary standard substance, potassium hydrogen phthalate (KHPth), whereas a constant amount of phenolphthalein was added to all the detection reservoirs. A sample solution containing NaOH was dropped onto the center of the μPAD and was allowed to spread to the reaction reservoirs where the KHPth neutralized it. When the amount of NaOH exceeded that of the KHPth in the reaction reservoirs, unneutralized hydroxide ion penetrated the detection reservoirs, resulting in a color reaction from the phenolphthalein. Therefore, the number of the detection reservoirs with no color change determined the concentration of the NaOH in the sample solution. The titration was completed within 1 min by visually determining the end point, which required neither instrumentation nor software. The volumes of the KHPth and phenolphthalein solutions added to the corresponding reservoirs were optimized to obtain reproducible and accurate results for the concentration of NaOH. The μPADs determined the concentration of NaOH at orders of magnitude ranging from 0.01 to 1 M. An acid sample, HCl, was also determined using Na2CO3 as a primary standard substance instead of KHPth. Furthermore, the μPAD was applicable to the titrations of nitric acid, sulfuric acid, acetic acid, and ammonia solutions. The μPADs were stable for more than 1 month when stored in darkness at room temperature, although this was reduced to only 5 days under daylight conditions. The analysis of acidic hot spring water was also demonstrated in the field using the μPAD, and the results agreed well with those obtained by classic acid-base titration.

  1. Guanine base stacking in G-quadruplex nucleic acids.

    PubMed

    Lech, Christopher Jacques; Heddi, Brahim; Phan, Anh Tuân

    2013-02-01

    G-quadruplexes constitute a class of nucleic acid structures defined by stacked guanine tetrads (or G-tetrads) with guanine bases from neighboring tetrads stacking with one another within the G-tetrad core. Individual G-quadruplexes can also stack with one another at their G-tetrad interface leading to higher-order structures as observed in telomeric repeat-containing DNA and RNA. In this study, we investigate how guanine base stacking influences the stability of G-quadruplexes and their stacked higher-order structures. A structural survey of the Protein Data Bank is conducted to characterize experimentally observed guanine base stacking geometries within the core of G-quadruplexes and at the interface between stacked G-quadruplex structures. We couple this survey with a systematic computational examination of stacked G-tetrad energy landscapes using quantum mechanical computations. Energy calculations of stacked G-tetrads reveal large energy differences of up to 12 kcal/mol between experimentally observed geometries at the interface of stacked G-quadruplexes. Energy landscapes are also computed using an AMBER molecular mechanics description of stacking energy and are shown to agree quite well with quantum mechanical calculated landscapes. Molecular dynamics simulations provide a structural explanation for the experimentally observed preference of parallel G-quadruplexes to stack in a 5'-5' manner based on different accessible tetrad stacking modes at the stacking interfaces of 5'-5' and 3'-3' stacked G-quadruplexes. PMID:23268444

  2. Acid-degradable polyurethane particles for protein-based vaccines

    PubMed Central

    Bachelder, Eric M.; Beaudette, Tristan T.; Broaders, Kyle E.; Paramonov, Sergey E.; Dashe, Jesse; Fréchet, Jean M. J.

    2009-01-01

    Acid-degradable particles containing a model protein antigen, ovalbumin, were prepared from a polyurethane with acetal moieties embedded throughout the polymer, and characterized by dynamic light scattering and transmission electron microscopy. The small molecule degradation by-product of the particles was synthesized and tested in vitro for toxicity indicating an LC50 of 12,500 μg/ml. A new liquid chromatography-mass spectrometry technique was developed to monitor the in vitro degradation of these particles. The degradation by-product inside RAW macrophages was at its highest level after 24 hours of culture and was efficiently exocytosed until it was no longer detectable after four days. When tested in vitro, these particles induced a substantial increase in the presentation of the immunodominant ovalbumin-derived peptide SIINFEKL in both macrophages and dendritic cells. In addition, vaccination with these particles generated a cytotoxic T-lymphocyte response that was superior to both free ovalbumin and particles made from an analogous but slower-degrading acid-labile polyurethane polymer. Overall, we present a fully degradable polymer system with non-toxic by-products, which may find use in various biomedical applications including protein-based vaccines. PMID:18710254

  3. Kinetics of acid base catalyzed transesterification of Jatropha curcas oil.

    PubMed

    Jain, Siddharth; Sharma, M P

    2010-10-01

    Out of various non-edible oil resources, Jatropha curcas oil (JCO) is considered as future feedstock for biodiesel production in India. Limited work is reported on the kinetics of transesterification of high free fatty acids containing oil. The present study reports the results of kinetic study of two-step acid base catalyzed transesterification process carried out at an optimum temperature of 65 °C and 50 °C for esterification and transesterification respectively under the optimum methanol to oil ratio of 3:7 (v/v), catalyst concentration 1% (w/w) for H₂SO₄ and NaOH. The yield of methyl ester (ME) has been used to study the effect of different parameters. The results indicate that both esterification and transesterification reaction are of first order with reaction rate constant of 0.0031 min⁻¹ and 0.008 min⁻¹ respectively. The maximum yield of 21.2% of ME during esterification and 90.1% from transesterification of pretreated JCO has been obtained.

  4. Water-wire catalysis in photoinduced acid-base reactions.

    PubMed

    Kwon, Oh-Hoon; Mohammed, Omar F

    2012-07-01

    The pronounced ability of water to form a hyperdense hydrogen (H)-bond network among itself is at the heart of its exceptional properties. Due to the unique H-bonding capability and amphoteric nature, water is not only a passive medium, but also behaves as an active participant in many chemical and biological reactions. Here, we reveal the catalytic role of a short water wire, composed of two (or three) water molecules, in model aqueous acid-base reactions synthesizing 7-hydroxyquinoline derivatives. Utilizing femtosecond-resolved fluorescence spectroscopy, we tracked the trajectories of excited-state proton transfer and discovered that proton hopping along the water wire accomplishes the reaction more efficiently compared to the transfer occurring with bulk water clusters. Our finding suggests that the directionality of the proton movements along the charge-gradient H-bond network may be a key element for long-distance proton translocation in biological systems, as the H-bond networks wiring acidic and basic sites distal to each other can provide a shortcut for a proton in searching a global minimum on a complex energy landscape to its destination.

  5. Fast high-throughput method for the determination of acidity constants by capillary electrophoresis: I. Monoprotic weak acids and bases.

    PubMed

    Fuguet, Elisabet; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martí

    2009-04-24

    A new and fast method to determine acidity constants of monoprotic weak acids and bases by capillary zone electrophoresis based on the use of an internal standard (compound of similar nature and acidity constant as the analyte) has been developed. This method requires only two electrophoretic runs for the determination of an acidity constant: a first one at a pH where both analyte and internal standard are totally ionized, and a second one at another pH where both are partially ionized. Furthermore, the method is not pH dependent, so an accurate measure of the pH of the buffer solutions is not needed. The acidity constants of several phenols and amines have been measured using internal standards of known pK(a), obtaining a mean deviation of 0.05 pH units compared to the literature values. PMID:19168179

  6. Fast high-throughput method for the determination of acidity constants by capillary electrophoresis: I. Monoprotic weak acids and bases.

    PubMed

    Fuguet, Elisabet; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martí

    2009-04-24

    A new and fast method to determine acidity constants of monoprotic weak acids and bases by capillary zone electrophoresis based on the use of an internal standard (compound of similar nature and acidity constant as the analyte) has been developed. This method requires only two electrophoretic runs for the determination of an acidity constant: a first one at a pH where both analyte and internal standard are totally ionized, and a second one at another pH where both are partially ionized. Furthermore, the method is not pH dependent, so an accurate measure of the pH of the buffer solutions is not needed. The acidity constants of several phenols and amines have been measured using internal standards of known pK(a), obtaining a mean deviation of 0.05 pH units compared to the literature values.

  7. An arbitrary correction function for CO(2) evolution in acid-base titrations and its use in multiparametric refinement of data.

    PubMed

    Wozniak, M; Nowogrocki, G

    1981-08-01

    A great number of acid-base titrations are performed under an inert gas flow: in the procedure, a variable amount of CO(2)-from carbonated reactants-is carried away and thus prevents strict application of mass-balance equations. A function for the CO(2) evolution is proposed and introduced into the general expression for the volume of titrant. Use of this expression in multiparametric refinement yields, besides the usual values (concentrations, acidity constants...), a parameter characteristic of this departure of CO(2). Furthermore, a modified weighting factor is introduced to take into account the departure from equilibrium caused by the slow CO(2) evolution. The validity of these functions was successfully tested on three typical examples: neutralization of strong acid by sodium carbonate, of sodium carbonate by strong acid, and of a mixture of hydrochloric acid, 4-nitrophenol and phenol by carbonated potassium hydroxide.

  8. Covalent triazine-based framework: A promising adsorbent for removal of perfluoroalkyl acids from aqueous solution.

    PubMed

    Wang, Bingyu; Lee, Linda S; Wei, Chenhui; Fu, Heyun; Zheng, Shourong; Xu, Zhaoyi; Zhu, Dongqiang

    2016-09-01

    Perfluoroalkyl acids (PFAAs) are highly stable, persistent, and ubiquitous in the environment with significant concerns growing with regards to both human and ecosystem health. Due to the high stability to both biological and chemical attack, the only currently feasible approach for their removal from water is adsorbent technology. The main objective of this study was to assess a covalent triazine-based framework (CTF) adsorbent for removal from aqueous solutions of perfluoro C4, C6, and C8 carboxylates and sulfonates including the two C8s most commonly monitored, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Adsorption affinity and capacity were quantified and compared to three commonly used sorbents: pulverized microporous activated carbon, single-walled carbon nanotubes, and Amberlite IRA-400 anion-exchange resin. CTF adsorbent exhibited pronouncedly higher adsorption affinity and capacity of PFAAs than other test sorbents. The remarkably strong adsorption to CTF can be attributed to the favored electrostatic interaction between the protonated triazine groups on the inner wall of the hydrophobic CTF pore and the negatively charged head groups of the PFAAs intercalated between the CTF layers. The homogeneous, nanosized pores (1.2 nm) of CTF hindered adsorption of a large-sized dissolved humic acid, thus minimizing the suppression of PFAA adsorption. Additionally, regeneration of CTF was easily accomplished by simply raising pH > 11, which inhibited the electrostatic adsorptive interaction of PFAAs. PMID:27389552

  9. Novel silver-based nanoclay as an antimicrobial in polylactic acid food packaging coatings.

    PubMed

    Busolo, Maria A; Fernandez, Patricia; Ocio, Maria J; Lagaron, Jose M

    2010-11-01

    This paper presents a comprehensive performance study of polylactic acid (PLA) biocomposites, obtained by solvent casting, containing a novel silver-based antimicrobial layered silicate additive for use in active food packaging applications. The silver-based nanoclay showed strong antimicrobial activity against Gram-negative Salmonella spp. Despite the fact that no exfoliation of the silver-based nanoclay in PLA was observed, as suggested by transmission electron microscopy (TEM) and wide angle X-ray scattering (WAXS) experiments, the additive dispersed nicely throughout the PLA matrix to a nanoscale, yielding nanobiocomposites. The films were highly transparent with enhanced water barrier and strong biocidal properties. Silver migration from the films to a slightly acidified water medium, considered an aggressive food simulant, was measured by stripping voltammetry. Silver migration accelerated after 6 days of exposure. Nevertheless, the study suggests that migration levels of silver, within the specific migration levels referenced by the European Food Safety Agency (EFSA), exhibit antimicrobial activity, supporting the potential application of this biocidal additive in active food-packaging applications to improve food quality and safety. PMID:20711905

  10. Soil microbes compete strongly with plants for soil inorganic and amino acid nitrogen in a semiarid grassland exposed to elevated CO2 and warming

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Free amino acids (FAAs) in soil are an important N source for plants, and abundances are predicted to shift under altered climate conditions such as elevated atmospheric CO2. Composition, plant uptake capacity and plant and microbial use of FAAs relative to inorganic N forms were investigated in a t...

  11. Spherical Nucleic Acids as Intracellular Agents for Nucleic Acid Based Therapeutics

    NASA Astrophysics Data System (ADS)

    Hao, Liangliang

    Recent functional discoveries on the noncoding sequences of human genome and transcriptome could lead to revolutionary treatment modalities because the noncoding RNAs (ncRNAs) can be applied as therapeutic agents to manipulate disease-causing genes. To date few nucleic acid-based therapeutics have been translated into the clinic due to challenges in the delivery of the oligonucleotide agents in an effective, cell specific, and non-toxic fashion. Unmodified oligonucleotide agents are destroyed rapidly in biological fluids by enzymatic degradation and have difficulty crossing the plasma membrane without the aid of transfection reagents, which often cause inflammatory, cytotoxic, or immunogenic side effects. Spherical nucleic acids (SNAs), nanoparticles consisting of densely organized and highly oriented oligonucleotides, pose one possible solution to circumventing these problems in both the antisense and RNA interference (RNAi) pathways. The unique three dimensional architecture of SNAs protects the bioactive oligonucleotides from unspecific degradation during delivery and supports their targeting of class A scavenger receptors and endocytosis via a lipid-raft-dependent, caveolae-mediated pathway. Owing to their unique structure, SNAs are able to cross cell membranes and regulate target genes expression as a single entity, without triggering the cellular innate immune response. Herein, my thesis has focused on understanding the interactions between SNAs and cellular components and developing SNA-based nanostructures to improve therapeutic capabilities. Specifically, I developed a novel SNA-based, nanoscale agent for delivery of therapeutic oligonucleotides to manipulate microRNAs (miRNAs), the endogenous post-transcriptional gene regulators. I investigated the role of SNAs involving miRNAs in anti-cancer or anti-inflammation responses in cells and in in vivo murine disease models via systemic injection. Furthermore, I explored using different strategies to construct

  12. Modeling description and spectroscopic evidence of surface acid-base properties of natural illites.

    PubMed

    Liu, W

    2001-12-01

    The acid-base properties of natural illites from different areas were studied by potentiometric titrations. The acidimetric supernatant was regarded as the system blank to calculate the surface site concentration due to consideration of substrate dissolution during the prolonged acidic titration. The following surface complexation model could give a good interpretation of the surface acid-base reactions of the aqueous illites:

  13. Dynamical Approach to Multiequilibria Problems for Mixtures of Acids and Their Conjugated Bases

    ERIC Educational Resources Information Center

    Glaser, Rainer E.; Delarosa, Marco A.; Salau, Ahmed Olasunkanmi; Chicone, Carmen

    2014-01-01

    Mathematical methods are described for the determination of steady-state concentrations of all species in multiequilibria systems consisting of several acids and their conjugated bases in aqueous solutions. The main example consists of a mixture of a diprotic acid H[subscript 2]A, a monoprotic acid HB, and their conjugate bases. The reaction…

  14. Ultrasonic and densimetric titration applied for acid-base reactions.

    PubMed

    Burakowski, Andrzej; Gliński, Jacek

    2014-01-01

    Classical acoustic acid-base titration was monitored using sound speed and density measurements. Plots of these parameters, as well as of the adiabatic compressibility coefficient calculated from them, exhibit changes with the volume of added titrant. Compressibility changes can be explained and quantitatively predicted theoretically in terms of Pasynski theory of non-compressible hydrates combined with that of the additivity of the hydration numbers with the amount and type of ions and molecules present in solution. It also seems that this development could be applied in chemical engineering for monitoring the course of chemical processes, since the applied experimental methods can be carried out almost independently on the medium under test (harmful, aggressive, etc.).

  15. Adansonian Analysis and Deoxyribonucleic Acid Base Composition of Serratia marcescens

    PubMed Central

    Colwell, R. R.; Mandel, M.

    1965-01-01

    Colwell, R. R. (Georgetown University, Washington, D.C.), and M. Mandel. Adansonian analysis and deoxyribonucleic acid base composition of Serratia marcescens. J. Bacteriol. 89:454–461. 1965.—A total of 33 strains of Serratia marcescens were subjected to Adansonian analysis for which more than 200 coded features for each of the organisms were included. In addition, the base composition [expressed as moles per cent guanine + cytosine (G + C)] of the deoxyribonucleic acid (DNA) prepared from each of the strains was determined. Except for four strains which were intermediate between Serratia and the Hafnia and Aerobacter group C of Edwards and Ewing, the S. marcescens species group proved to be extremely homogeneous, and the different strains showed high affinities for each other (mean similarity, ¯S = 77%). The G + C ratio of the DNA from the Serratia strains ranged from 56.2 to 58.4% G + C. Many species names have been listed for the genus, but only a single clustering of the strains was obtained at the species level, for which the species name S. marcescens was retained. S. kiliensis, S. indica, S. plymuthica, and S. marinorubra could not be distinguished from S. marcescens; it was concluded, therefore, that there is only a single species in the genus. The variety designation kiliensis does not appear to be valid, since no subspecies clustering of strains with negative Voges-Proskauer reactions could be detected. The characteristics of the species are listed, and a description of S. marcescens is presented. PMID:14255714

  16. Are carboxyl groups the most acidic sites in amino acids? Gas-phase acidities, photoelectron spectra, and computations on tyrosine, p-hydroxybenzoic acid, and their conjugate bases.

    PubMed

    Tian, Zhixin; Wang, Xue-Bin; Wang, Lai-Sheng; Kass, Steven R

    2009-01-28

    Deprotonation of tyrosine in the gas phase was found to occur preferentially at the phenolic site, and the conjugate base consists of a 70:30 mixture of phenoxide and carboxylate anions at equilibrium. This result was established by developing a chemical probe for differentiating these two isomers, and the presence of both ions was confirmed by photoelectron spectroscopy. Equilibrium acidity measurements on tyrosine indicated that deltaG(acid)(o) = 332.5 +/- 1.5 kcal mol(-1) and deltaH(acid)(o) = 340.7 +/- 1.5 kcal mol(-1). Photoelectron spectra yielded adiabatic electron detachment energies of 2.70 +/- 0.05 and 3.55 +/- 0.10 eV for the phenoxide and carboxylate anions, respectively. The H/D exchange behavior of deprotonated tyrosine was examined using three different alcohols (CF3CH2OD, C6H5CH2OD, and CH3CH2OD), and incorporation of up to three deuterium atoms was observed. Two pathways are proposed to account for these results, and all of the experimental findings are supplemented with B3LYP/aug-cc-pVDZ and G3B3 calculations. In addition, it was found that electrospray ionization of tyrosine from a 3:1 (v/v) CH3OH/H2O solution using a commercial source produces a deprotonated [M-H]- anion with the gas-phase equilibrium composition rather than the structure of the ion that exists in aqueous media. Electrospray ionization from acetonitrile, however, leads largely to the liquid-phase (carboxylate) structure. A control molecule, p-hydroxybenzoic acid, was found to behave in a similar manner. Thus, the electrospray conditions that are employed for the analysis of a compound can alter the isomeric composition of the resulting anion.

  17. Nanoconstructions Based on Spatially Ordered Nucleic Acid Molecules

    NASA Astrophysics Data System (ADS)

    Yevdokimov, Yu. M.

    Different strategies for the design of nanoconstructions whose building blocks are both linear molecules of double-stranded nucleic acids and nucleic acid molecules fixed in the spatial structure of particles of liquid-crystalline dispersions are described.

  18. Amine-based systems for carboxylic acid recovery

    SciTech Connect

    King, C.J.

    1992-05-01

    Several carboxylic acids are prominent commercial products, and their number and importance will probably grow. Getting these acids out of aqueous solution is necessary in petrochemical manufacture, fermentation, and the environmentally and economically important recovery from waste streams. In this paper, the authors discuss the methods possible to extract acids such as citric, lactic, and succinic from complex mixtures. Carboxylic acids are also readily made by fermentation and are among the most attractive substances that could be manufactured from biomass. Branches of this cycle lead to acetic, lactic, propionic, and formic acids, among others. Carboxylic acids are promising intermediates in a bioprocessing complex, because the oxygen of the biomass is placed in a form that is useful for further reaction with many other products. Citric acid is manufactured on a large scale by fermentation, and lactic and fumaric acids, among others, were manufactured that way in the past.

  19. Biotechnological routes based on lactic acid production from biomass.

    PubMed

    Gao, Chao; Ma, Cuiqing; Xu, Ping

    2011-01-01

    Lactic acid, the most important hydroxycarboxylic acid, is now commercially produced by the fermentation of sugars present in biomass. In addition to its use in the synthesis of biodegradable polymers, lactic acid can be regarded as a feedstock for the green chemistry of the future. Different potentially useful chemicals such as pyruvic acid, acrylic acid, 1,2-propanediol, and lactate ester can be produced from lactic acid via chemical and biotechnological routes. Here, we reviewed the current status of the production of potentially valuable chemicals from lactic acid via biotechnological routes. Although some of the reactions described in this review article are still not applicable at current stage, due to their "greener" properties, biotechnological processes for the production of lactic acid derivatives might replace the chemical routes in the future. PMID:21846500

  20. Microgel Tethering For Microarray-Based Nucleic Acid Diagnostics

    NASA Astrophysics Data System (ADS)

    Dai, Xiaoguang

    Molecular diagnostics (MDx) have radically changed the process of clinical microbial identification based on identifying genetic information, MDx approaches are both specific and fast. They can identify microbes to the species and strain level over a time scale that can be as short as one hour. With such information clinicians can administer the most effective and appropriate antimicrobial treatment at an early time point with substantial implications both for patient well-being and for easing the burden on the health-care system. Among the different MDx approaches, such as fluorescence in-situ hybridization, microarrays, next-generation sequencing, and mass spectrometry, point-of-care MDx platforms are drawing particular interest due to their low cost, robustness, and wide application. This dissertation develops a novel MDx technology platform capable of high target amplification and detection performance. For nucleic acid target detection, we fabricate an array of electron-beam-patterned microgels on a standard glass microscope slide. The microgels can be as small as a few hundred nanometers. The unique way of energy deposition during electron-beam lithography provides the microgels with a very diffuse water -gel interface that enables them to not only serve as substrates to immobilize DNA probes but do so while preserving them in a highly hydrated environment that optimizes their performance. Benefiting from the high spatial resolution provided by such techniques as position-sensitive microspotting and dip-pen nanolithography, multiple oligonucleotide probes known as molecular beacons (MBs) can be patterned on microgels. Furthermore, nucleic acid target amplification can be conducted in direct contact with the microgel-tethered detection array. Specifically, we use an isothermal RNA amplification reaction - nucleic acid sequence-based amplification (NASBA). ssRNA amplicons of from the NASBA reaction can directly hybridize with microgel-tethered MBs, and the

  1. Improved physical stability of amorphous state through acid base interactions.

    PubMed

    Telang, Chitra; Mujumdar, Siddharthya; Mathew, Michael

    2009-06-01

    To investigate role of specific interactions in aiding formation and stabilization of amorphous state in ternary and binary dispersions of a weakly acidic drug. Indomethacin (IMC), meglumine (MU), and polyvinyl pyrollidone (PVP) were the model drug, base, and polymer, respectively. Dispersions were prepared using solvent evaporation. Physical mixtures were cryogenically coground. XRPD, PLM, DSC, TGA, and FTIR were used for characterization. MU has a high crystallization tendency and is characterized by a low T(g) (17 degrees C). IMC crystallization was inhibited in ternary dispersion with MU compared to IMC/PVP alone. An amorphous state formed readily even in coground mixtures. Spectroscopic data are indicative of an IMC-MU amorphous salt and supports solid-state proton transfer. IMC-MU salt displays a low T(g) approximately 50 degrees C, but is more physically stable than IMC, which in molecular mixtures with MU, resisted crystallization even when present in stoichiometric excess of base. This is likely due to a disrupted local structure of amorphous IMC due to specific interactions. IMC showed improved physical stability on incorporating MU in polymer, in spite of low T(g) of the base indicating that chemical interactions play a dominant role in physical stabilization. Salt formation could be induced thermally and mechanically.

  2. Acid-base transport by the renal proximal tubule

    PubMed Central

    Skelton, Lara A.; Boron, Walter F.; Zhou, Yuehan

    2015-01-01

    Each day, the kidneys filter 180 L of blood plasma, equating to some 4,300 mmol of the major blood buffer, bicarbonate (HCO3−). The glomerular filtrate enters the lumen of the proximal tubule (PT), and the majority of filtered HCO3− is reclaimed along the early (S1) and convoluted (S2) portions of the PT in a manner coupled to the secretion of H+ into the lumen. The PT also uses the secreted H+ to titrate non-HCO3− buffers in the lumen, in the process creating “new HCO3−” for transport into the blood. Thus, the PT – along with more distal renal segments – is largely responsible for regulating plasma [HCO3−]. In this review we first focus on the milestone discoveries over the past 50+ years that define the mechanism and regulation of acid-base transport by the proximal tubule. Further on in the review, we will summarize research still in progress from our laboratory, work that addresses the problem of how the PT is able to finely adapt to acid–base disturbances by rapidly sensing changes in basolateral levels of HCO3− and CO2 (but not pH), and thereby to exert tight control over the acid–base composition of the blood plasma. PMID:21170887

  3. [Determination of body fluid based on analysis of nucleic acids].

    PubMed

    Korabečná, Marie

    2015-01-01

    Recent methodological approaches of molecular genetics allow isolation of nucleic acids (DNA and RNA) from negligible forensic samples. Analysis of these molecules may be used not only for individual identification based on DNA profiling but also for the detection of origin of the body fluid which (alone or in mixture with other body fluids) forms the examined biological trace. Such an examination can contribute to the evaluation of procedural, technical and tactical value of the trace. Molecular genetic approaches discussed in the review offer new possibilities in comparison with traditional spectrum of chemical, immunological and spectroscopic tests especially with regard to the interpretation of mixtures of biological fluids and to the confirmatory character of the tests. Approaches based on reverse transcription of tissue specific mRNA and their subsequent polymerase chain reaction (PCR) and fragmentation analysis are applicable on samples containing minimal amounts of biological material. Methods for body fluid discrimination based on examination of microRNA in samples provided so far confusing results therefore further development in this field is needed. The examination of tissue specific methylation of nucleotides in selected gene sequences seems to represent a promising enrichment of the methodological spectrum. The detection of DNA sequences of tissue related bacteria has been established and it provides satisfactory results mainly in combination with above mentioned methodological approaches. PMID:26419517

  4. Modeling uranium transport in acidic contaminated groundwater with base addition

    SciTech Connect

    Zhang, Fan; Luo, Wensui; Parker, Jack C.; Brooks, Scott C; Watson, David B; Jardine, Philip; Gu, Baohua

    2011-01-01

    This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

  5. Modeling uranium transport in acidic contaminated groundwater with base addition.

    PubMed

    Zhang, Fan; Luo, Wensui; Parker, Jack C; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2011-06-15

    This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO(3)(-), SO(4)(2-), U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

  6. Methylene-bis[(aminomethyl)phosphinic acids]: synthesis, acid-base and coordination properties.

    PubMed

    David, Tomáš; Procházková, Soňa; Havlíčková, Jana; Kotek, Jan; Kubíček, Vojtěch; Hermann, Petr; Lukeš, Ivan

    2013-02-21

    Three symmetrical methylene-bis[(aminomethyl)phosphinic acids] bearing different substituents on the central carbon atom, (NH(2)CH(2))PO(2)H-C(R(1))(R(2))-PO(2)H(CH(2)NH(2)) where R(1) = OH, R(2) = Me (H(2)L(1)), R(1) = OH, R(2) = Ph (H(2)L(2)) and R(1),R(2) = H (H(2)L(3)), were synthesized. Acid-base and complexing properties of the ligands were studied in solution as well as in the solid state. The ligands show unusually high basicity of the nitrogen atoms (log K(1) = 9.5-10, log K(2) = 8.5-9) if compared with simple (aminomethyl)phosphinic acids and, consequently, high stability constants of the complexes with studied divalent metal ions. The study showed the important role of the hydroxo group attached to the central carbon atom of the geminal bis(phosphinate) moiety. Deprotonation of the hydroxo group yields the alcoholate anion which tends to play the role of a bridging ligand and induces formation of polynuclear complexes. Solid-state structures of complexes [H(2)N=C(NH(2))(2)][Cu(2)(H(-1)L(2))(2)]CO(3)·10H(2)O and Li(2)[Co(4)(H(-1)L(1))(3)(OH)]·17.5H(2)O were determined by X-ray diffraction. The complexes show unexpected geometries forming dinuclear and cubane-like structures, respectively. The dinuclear copper(II) complex contains a bridging μ(2)-alcoholate group with the (-)O-P(=O)-CH(2)-NH(2) fragments of each ligand molecule chelated to the different central ion. In the cubane cobalt(II) complex, one μ(3)-hydroxide and three μ(3)-alcoholate anions are located in the cube vertices and both phosphinate groups of one ligand molecule are chelating the same cobalt(II) ion while each of its amino groups are bound to different neighbouring metal ions. All such three metal ions are bridged by the alcoholate group of a given ligand.

  7. Tin film sensor with on-chip three-electrode configuration for voltammetric determination of trace Tl(I) in strong acidic media.

    PubMed

    Kokkinos, Christos; Economou, Anastasios

    2014-07-01

    The present work describes the trace analysis of Tl(I) in acidic medium (0.05 mol L(-1) nitric acid) by square wave anodic stripping voltammetry (SWASV) at a tin film sensor with novel configuration. This "green" electroanalytical device features on-chip metal film electrodes (a Sn-film working electrode, a Ag-film reference electrode and a Pt-film counter electrode), fabricated by sputtering the respective metals on a silicon chip. The effect of preconcentration time, preconcentration potential and SW stripping parameters on the Tl(I) detection was studied in detail. The limit of detection for Tl(I) was 1.1 μg L(-1), while the % relative standard deviation at the same sensor was 5.2% at the 10 μg L(-1) level. Finally, the sensors were successfully applied to the direct determination of Tl(I) in an acidified certified lake water sample. PMID:24840436

  8. Tin film sensor with on-chip three-electrode configuration for voltammetric determination of trace Tl(I) in strong acidic media.

    PubMed

    Kokkinos, Christos; Economou, Anastasios

    2014-07-01

    The present work describes the trace analysis of Tl(I) in acidic medium (0.05 mol L(-1) nitric acid) by square wave anodic stripping voltammetry (SWASV) at a tin film sensor with novel configuration. This "green" electroanalytical device features on-chip metal film electrodes (a Sn-film working electrode, a Ag-film reference electrode and a Pt-film counter electrode), fabricated by sputtering the respective metals on a silicon chip. The effect of preconcentration time, preconcentration potential and SW stripping parameters on the Tl(I) detection was studied in detail. The limit of detection for Tl(I) was 1.1 μg L(-1), while the % relative standard deviation at the same sensor was 5.2% at the 10 μg L(-1) level. Finally, the sensors were successfully applied to the direct determination of Tl(I) in an acidified certified lake water sample.

  9. Amino acid-bile acid based molecules: extremely narrow surfactant nanotubes formed by a phenylalanine-substituted cholic acid.

    PubMed

    Travaglini, Leana; D'Annibale, Andrea; Schillén, Karin; Olsson, Ulf; Sennato, Simona; Pavel, Nicolae V; Galantini, Luciano

    2012-12-21

    An amino acid-substituted bile acid forms tubular aggregates with inner and outer diameters of about 3 and 6 nm. The diameters are unusually small for surfactant self-assembled tubes. The results enhance the spectrum of applications of supramolecular tubules and open up possibilities for investigating a novel class of biological amphiphiles.

  10. Acid-base and copper-binding properties of three organic matter fractions isolated from a forest floor soil solution

    NASA Astrophysics Data System (ADS)

    van Schaik, Joris W. J.; Kleja, Dan B.; Gustafsson, Jon Petter

    2010-02-01

    Vast amounts of knowledge about the proton- and metal-binding properties of dissolved organic matter (DOM) in natural waters have been obtained in studies on isolated humic and fulvic (hydrophobic) acids. Although macromolecular hydrophilic acids normally make up about one-third of DOM, their proton- and metal-binding properties are poorly known. Here, we investigated the acid-base and Cu-binding properties of the hydrophobic (fulvic) acid fraction and two hydrophilic fractions isolated from a soil solution. Proton titrations revealed a higher total charge for the hydrophilic acid fractions than for the hydrophobic acid fraction. The most hydrophilic fraction appeared to be dominated by weak acid sites, as evidenced by increased slope of the curve of surface charge versus pH at pH values above 6. The titration curves were poorly predicted by both Stockholm Humic Model (SHM) and NICA-Donnan model calculations using generic parameter values, but could be modelled accurately after optimisation of the proton-binding parameters (pH ⩽ 9). Cu-binding isotherms for the three fractions were determined at pH values of 4, 6 and 9. With the optimised proton-binding parameters, the SHM model predictions for Cu binding improved, whereas the NICA-Donnan predictions deteriorated. After optimisation of Cu-binding parameters, both models described the experimental data satisfactorily. Iron(III) and aluminium competed strongly with Cu for binding sites at both pH 4 and pH 6. The SHM model predicted this competition reasonably well, but the NICA-Donnan model underestimated the effects significantly at pH 6. Overall, the Cu-binding behaviour of the two hydrophilic acid fractions was very similar to that of the hydrophobic acid fraction, despite the differences observed in proton-binding characteristics. These results show that for modelling purposes, it is essential to include the hydrophilic acid fraction in the pool of 'active' humic substances.

  11. Identification of gallic acid based glycoconjugates as a novel tubulin polymerization inhibitors.

    PubMed

    Upadhyaya, Kapil; Hamidullah; Singh, Kartikey; Arun, Ashutosh; Shukla, Mahendra; Srivastava, Neetika; Ashraf, Raghib; Sharma, Abhisheak; Mahar, Rohit; Shukla, Sanjeev K; Sarkar, Jayanta; Ramachandran, Ravishankar; Lal, Jawahar; Konwar, Rituraj; Tripathi, Rama Pati

    2016-01-28

    A novel class of gallic acid based glycoconjugates were designed and synthesized as potential anticancer agents. Among all the compounds screened, compound 2a showed potent anticancer activity against breast cancer cells. The latter resulted in tubulin polymerization inhibition and induced G2/M cell cycle arrest, generation of reactive oxygen species, mitochondrial depolarization and subsequent apoptosis in breast cancer cells. In addition, ultraviolet-visible spectroscopy and fluorescence quenching studies of the compound with tubulin confirmed direct interaction of compounds with tubulin. Molecular modeling studies revealed that it binds at the colchicine binding site in tubulin. Further, 2a also exhibited potent in vivo anticancer activity in LA-7 syngeneic rat mammary tumor model. Current data projects its strong candidature to be developed as anticancer agent.

  12. Unified molecular picture of the surfaces of aqueous acid, base, and salt solutions.

    PubMed

    Mucha, Martin; Frigato, Tomaso; Levering, Lori M; Allen, Heather C; Tobias, Douglas J; Dang, Liem X; Jungwirth, Pavel

    2005-04-28

    The molecular structure of the interfacial regions of aqueous electrolytes is poorly understood, despite its crucial importance in many biological, technological, and atmospheric processes. A long-term controversy pertains between the standard picture of an ion-free surface layer and the strongly ion specific behavior indicating in many cases significant propensities of simple inorganic ions for the interface. Here, we present a unified and consistent view of the structure of the air/solution interface of aqueous electrolytes containing monovalent inorganic ions. Molecular dynamics calculations show that in salt solutions and bases the positively charged ions, such as alkali cations, are repelled from the interface, whereas the anions, such as halides or hydroxide, exhibit a varying surface propensity, correlated primarily with the ion polarizability and size. The behavior of acids is different due to a significant propensity of hydronium cations for the air/solution interface. Therefore, both cations and anions exhibit enhanced concentrations at the surface and, consequently, these acids (unlike bases and salts) reduce the surface tension of water. The results of the simulations are supported by surface selective nonlinear vibrational spectroscopy, which reveals among other things that the hydronium cations are present at the air/solution interface. The ion specific propensities for the air/solution interface have important implications for a whole range of heterogeneous physical and chemical processes, including atmospheric chemistry of aerosols, corrosion processes, and bubble coalescence.

  13. Swelling behaviors of porous lignin based poly (acrylic acid).

    PubMed

    Ma, Yanli; Sun, Yajie; Fu, Yujie; Fang, Guizhen; Yan, Xingru; Guo, Zhanhu

    2016-11-01

    Supramolecular cross-linked porous lignin based poly (acrylic acid) [LBPAA] was lab-synthesized by copolymerizing lignin grafted N, N'-methylene-bisacrylamide (LM) and acrylic acid. LBPAA successfully acted as a water retention agent with salt resistance and biodegradation for agricultural applications. Lignin was found to improve its swelling behaviors with higher water retention, fast swelling and de-swelling rates. The salt tolerance was stronger in the case of LBPAA (60 PAA/40 LM) [60 wt% PAA/40 wt% LM], i.e., 145.79 g·g(-1) higher than PAA at 0.09 mM KCl solution. The effect of ion charges on the LBPAA swelling ratio was greater than that of ionic radius. The weight loss of LBPAA (60 PAA/40 LM) was 5.47%, 4.96%, and 4.56% in the soil of Tangshan, Harbin, and Sian, respectively. The soil moisture content and clay content were observed to decrease gradually with increasing the burial time. The biodegradation test of LBPAA (60 PAA/40 LM) composite exhibited different bacterial colony forming units (CFU), the soil of Tangshan was 2.0 × 10(3) CFU·g(-1) soil, 7.0 × 10(3) CFU·g(-1) soil for Harbin, and 6.10 × 10(4) CFU·g(-1) soil for Sian. However, the organic matter contents in the soils did not have significant changes (Tangshan 6.21 mg·g(-1), Harbin 0.61 mg·g(-1), and Sian 0.405 mg·g(-1)). PMID:27587327

  14. Electrospun poly(lactic acid) based conducting nanofibrous networks

    NASA Astrophysics Data System (ADS)

    Patra, S. N.; Bhattacharyya, D.; Ray, S.; Easteal, A. J.

    2009-08-01

    Multi-functionalised micro/nanostructures of conducting polymers in neat or blended forms have received much attention because of their unique properties and technological applications in electrical, magnetic and biomedical devices. Biopolymer-based conducting fibrous mats are of special interest for tissue engineering because they not only physically support tissue growth but also are electrically conductive, and thus are able to stimulate specific cell functions or trigger cell responses. They are effective for carrying current in biological environments and can thus be considered for delivering local electrical stimuli at the site of damaged tissue to promote wound healing. Electrospinning is an established way to process polymer solutions or melts into continuous fibres with diameter often in the nanometre range. This process primarily depends on a number of parameters, including the type of polymer, solution viscosity, polarity and surface tension of the solvent, electric field strength and the distance between the spinneret and the collector. The present research has included polyaniline (PANi) as the conducting polymer and poly(L-lactic acid) (PLLA) as the biopolymer. Dodecylbenzene sulphonic acid (DBSA) doped PANi and PLLA have been dissolved in a common solvent (mixtures of chloroform and dimethyl formamide (DMF)), and the solutions successfully electrospun. DMF enhanced the dielectric constant of the solvent, and tetra butyl ammonium bromide (TBAB) was used as an additive to increase the conductivity of the solution. DBSA-doped PANi/PLLA mat exhibits an almost bead-free network of nanofibres that have extraordinarily smooth surface and diameters in the range 75 to 100 nm.

  15. Solution influence on biomolecular equilibria - Nucleic acid base associations

    NASA Technical Reports Server (NTRS)

    Pohorille, A.; Pratt, L. R.; Burt, S. K.; Macelroy, R. D.

    1984-01-01

    Various attempts to construct an understanding of the influence of solution environment on biomolecular equilibria at the molecular level using computer simulation are discussed. First, the application of the formal statistical thermodynamic program for investigating biomolecular equilibria in solution is presented, addressing modeling and conceptual simplications such as perturbative methods, long-range interaction approximations, surface thermodynamics, and hydration shell. Then, Monte Carlo calculations on the associations of nucleic acid bases in both polar and nonpolar solvents such as water and carbon tetrachloride are carried out. The solvent contribution to the enthalpy of base association is positive (destabilizing) in both polar and nonpolar solvents while negative enthalpies for stacked complexes are obtained only when the solute-solute in vacuo energy is added to the total energy. The release upon association of solvent molecules from the first hydration layer around a solute to the bulk is accompanied by an increase in solute-solvent energy and decrease in solvent-solvent energy. The techniques presented are expectd to displace less molecular and more heuristic modeling of biomolecular equilibria in solution.

  16. Ligation with nucleic acid sequence-based amplification.

    PubMed

    Ong, Carmichael; Tai, Warren; Sarma, Aartik; Opal, Steven M; Artenstein, Andrew W; Tripathi, Anubhav

    2012-01-01

    This work presents a novel method for detecting nucleic acid targets using a ligation step along with an isothermal, exponential amplification step. We use an engineered ssDNA with two variable regions on the ends, allowing us to design the probe for optimal reaction kinetics and primer binding. This two-part probe is ligated by T4 DNA Ligase only when both parts bind adjacently to the target. The assay demonstrates that the expected 72-nt RNA product appears only when the synthetic target, T4 ligase, and both probe fragments are present during the ligation step. An extraneous 38-nt RNA product also appears due to linear amplification of unligated probe (P3), but its presence does not cause a false-positive result. In addition, 40 mmol/L KCl in the final amplification mix was found to be optimal. It was also found that increasing P5 in excess of P3 helped with ligation and reduced the extraneous 38-nt RNA product. The assay was also tested with a single nucleotide polymorphism target, changing one base at the ligation site. The assay was able to yield a negative signal despite only a single-base change. Finally, using P3 and P5 with longer binding sites results in increased overall sensitivity of the reaction, showing that increasing ligation efficiency can improve the assay overall. We believe that this method can be used effectively for a number of diagnostic assays. PMID:22449695

  17. A physicochemical model of crystalloid infusion on acid-base status.

    PubMed

    Omron, Edward M; Omron, Rodney M

    2010-09-01

    The objective of this study is to develop a physicochemical model of the projected change in standard base excess (SBE) consequent to the infused volume of crystalloid solutions in common use. A clinical simulation of modeled acid-base and fluid compartment parameters was conducted in a 70-kg test participant at standard physiologic state: pH =7.40, partial pressure of carbon dioxide (PCO2) = 40 mm Hg, Henderson-Hasselbalch actual bicarbonate ([HCO3]HH) = 24.5 mEq/L, strong ion difference (SID) = 38.9 mEq/L, albumin = 4.40 g/dL, inorganic phosphate = 1.16 mmol/L, citrate total = 0.135 mmol/L, and SBE =0.1 mEq/L. Simulations of multiple, sequential crystalloid infusions up to 10 L were conducted of normal saline (SID = 0), lactated Ringer's (SID = 28), plasmalyte 148 (SID = 50), one-half normal saline þ 75 mEq/L sodium bicarbonate (NaHCO3; SID = 75), 0.15 mol/L NaHCO3 (SID = 150), and a hypothetical crystalloid solution whose SID = 24.5 mEq/L, respectively. Simulations were based on theoretical completion of steady-state equilibrium and PCO2 was fixed at 40 mm Hg to assess nonrespiratory acid-base effects. A crystalloid SID equivalent to standard state actual bicarbonate (24.5 mEq/L) results in a neutral metabolic acid-base status for infusions up to 10 L. The 5 study solutions exhibited curvilinear relationships between SBE and crystalloid infusion volume in liters. Solutions whose SID was greater than 24.5 mEq/L demonstrated a progressive metabolic alkalosis and less, a progressive metabolic acidosis. In a human model system, the effects of crystalloid infusion on SBE are a function of the crystalloid and plasma SID, volume infused, and nonvolatile plasma weak acid changes. A projection of the impact of a unit volume of various isotonic crystalloid solutions on SBE is presented. The model's validation, applications, and limitations are examined.

  18. GPU-Based Implementations of the Noniterative Regularized-CCSD(T) Corrections: Applications to Strongly Correlated Systems.

    PubMed

    Ma, Wenjing; Krishnamoorthy, Sriram; Villa, Oreste; Kowalski, Karol

    2011-05-10

    The details of the graphical processing unit (GPU) implementation of the most computationally intensive (T)-part of the recently introduced regularized CCSD(T) (Reg-CCSD(T)) method [ Kowalski , K. ; Valiev , M. J. Chem. Phys. 2009 , 131 , 234107 ] for calculating electronic energies of strongly correlated systems are discussed. Parallel tests performed for several molecular systems show very good scalability of the triples part of the Reg-CCSD(T) approach. We also discuss the performance of the Reg-CCSD(T) GPU implementation as a function of the parameters defining the partitioning of the spinorbital domain (tiling structure). The accuracy of the Reg-CCSD(T) method is illustrated on three examples: the methyfluoride molecule, dissociation of dodecane, and open-shell Spiro cation (5,5'(4H,4H')-spirobi[cyclopenta[c]pyrrole] 2,2',6,6'-tetrahydro cation), which is a frequently used model to study electron transfer processes. It is demonstrated that a simple regularization of the cluster amplitudes used in the noniterative corrections accounting for the effect of triply excited configurations significantly improves the accuracies of ground-state energies in the presence of strong quasidegeneracy effects. For methylfluoride, we compare the Reg-CCSD(T) results with the CR-CC(2,3) and CCSDT energies, whereas for Spiro cation we compare Reg-CCSD(T) results with the energies obtained with completely renormalized CCSD(T) method. Performance tests for the Spiro, dodecane, and uracil molecules are also discussed. PMID:26610126

  19. Dynamics of a two-level system under strong driving: Quantum-gate optimization based on Floquet theory

    NASA Astrophysics Data System (ADS)

    Deng, Chunqing; Shen, Feiruo; Ashhab, Sahel; Lupascu, Adrian

    2016-09-01

    We consider the dynamics of a two-level system (qubit) driven by strong and short resonant pulses in the framework of Floquet theory. First we derive analytical expressions for the quasienergies and Floquet states of the driven system. If the pulse amplitude varies very slowly, the system adiabatically follows the instantaneous Floquet states, which acquire dynamical phases that depend on the evolution of the quasienergies over time. The difference between the phases acquired by the two Floquet states corresponds to a qubit state rotation, generalizing the notion of Rabi oscillations to the case of large driving amplitudes. If the pulse amplitude changes very fast, the evolution is nonadiabatic, with transitions taking place between the Floquet states. We quantify and analyze the nonadiabatic transitions during the pulse by employing adiabatic perturbation theory and exact numerical simulations. We find that, for certain combinations of pulse rise and fall times and maximum driving amplitude, a destructive interference effect leads to a remarkably strong suppression of transitions between the Floquet states. This effect provides the basis of a quantum control protocol, which we name Floquet interference efficient suppression of transitions in the adiabatic basis (FIESTA), that can be used to design ultrafast high-fidelity single-qubit quantum gates.

  20. The profile of volatile compounds in the outer and inner parts of broiled pork neck is strongly influenced by the acetic-acid marination conditions.

    PubMed

    Biller, Elżbieta; Boselli, Emanuele; Obiedziński, Mieczysław; Karpiński, Piotr; Waszkiewicz-Robak, Bożena

    2016-11-01

    Raw pork neck cutlets were marinated in an aqueous solution of acetic acid (pH4, 24h, 4°C) without (M) or with 1% (w/w) of glucose. The control (K) was formed by non-treated raw pork neck. The cutlets were then broiled (185°C, 30min). In all K cutlets, significant higher amounts of volatile compounds (VCs) were developed after broiling than the other samples. Significant more aldehydes and alcohols were present in the inner parts than in the surface. The correlation between surface and internal layers was high only for aldehydes. Marinating decreased the differences among VCs and led to the standardization of the processed meat. The addition of glucose to the marinade led to more volatile aldehydes, carboxylic acids, esters, furan, pyran, pyrazine, pyrrol and pyridine derivatives than in M samples. Several (53) specific VCs explained the differences among the surface samples related to the marinating process. However, only 16 VCs explained the variance among the inner parts. PMID:27395822

  1. Effect of acid-base alterations on hepatic lactate utilization

    PubMed Central

    Goldstein, Philip J.; Simmons, Daniel H.; Tashkin, Donald P.

    1972-01-01

    1. The effect of acid-base changes on hepatic lactate utilization was investigated in anaesthetized, mechanically ventilated dogs. 2. Portal vein flow and hepatic artery flow were measured with electromagnetic flowmeters, lactate concentration of portal vein, arterial and mixed hepatic venous blood was determined by an enzymatic technique, and hepatic lactate uptake was calculated using the Fick principle. 3. Respiratory alkalosis (Δ pH 0·25 ± 0·02) in four dogs resulted in a significant fall in total hepatic blood flow (-22 ± 4%) and a significant rise in both arterial lactate concentration (2·18 ± 0·32 m-mole/l.) and hepatic lactate utilization (3·9 ± 1·2 μmole/min.kg). 4. 0·6 M-Tris buffer infusion (Δ pH 0·21 ± 0·02) in four dogs produced no significant changes in liver blood flow, arterial lactate concentration or hepatic lactate uptake. 5. Respiratory acidosis (Δ pH -0·20 ± 0·03) in six dogs and metabolic acidosis (Δ pH -0·20 ± 0·02) in four dogs produced no significant changes in liver blood flow, decreases in arterial lactate concentration of 0·38 ± 0·09 m-mole/l. (P < 0·05) and 0·13 ± 0·13 m-mole/l., respectively, and no significant changes in hepatic lactate uptake. 6. A significant correlation (r = 0·63; P < 0·01) was found between hepatic lactate utilization and arterial lactate concentration during the hyperlactataemia associated with respiratory alkalosis. 7. Hyperlactataemia induced in four dogs by infusion of buffered sodium lactate (Δ pH 0·05 ± 0·01;% Δ liver blood flow 29 ± 7%) was also significantly correlated with hepatic lactate utilization (r = 0·70; P < 0·01) and the slope of the regression was similar to that during respiratory alkalosis. 8. These data suggest that the hyperlactataemia of alkalosis is not due to impaired hepatic utilization of lactate and that the principal determinant of hepatic lactate uptake during alkalosis or lactate infusion is blood lactate concentration, rather than liver

  2. Ultrastructural observation of the acid-base resistant zone of all-in-one adhesives using three different acid-base challenges.

    PubMed

    Tsujimoto, Miho; Nikaido, Toru; Inoue, Go; Sadr, Alireza; Tagami, Junji

    2010-11-01

    The aim of this study was to analyze the ultrastructure of the dentin-adhesive interface using two all-in-one adhesive systems (Clearfil Tri-S Bond, TB; Tokuyama Bond Force, BF) after different acid-base challenges. Three solutions were used as acidic solutions for the acid-base challenges: a demineralizing solution (DS), a phosphoric acid solution (PA), and a hydrochloric acid solution (HCl). After the acid-base challenges, the bonded interfaces were examined by scanning electron microscopy. Thickness of the acid-base resistant zone (ABRZ) created in PA and HCl was thinner than in DS for both adhesive systems. For BF adhesive, an eroded area was observed beneath the ABRZ after immersion in PA and HCl, but not in DS. Conversely for TB adhesive, the eroded area was observed only after immersion in PA. In conclusion, although the ABRZ was observed for both all-in-one adhesive systems, its morphological features were influenced by the ingredients of both the adhesive material and acidic solution.

  3. Mechanism of sorption sulpho-derivative organic chelating agents on strong base anion exchanger Amberlite IRA-402 by FT-IR/PAS and DRS methods

    NASA Astrophysics Data System (ADS)

    Wronski, G.; Pasieczna-Patkowska, S.; Hubicki, Z.

    2008-02-01

    In the paper, strong base anion exchanger Amberlite IRA-402 was modified by using sulpho-derivative organic chelating agents as: Brilliant Yellow, Xylenol Orange, Bromophenyl Blue. The investigations exhibited, that anion exchanger Amberlite IRA-402 is modified very simply by organic chelating agents (working capacity 0.25 0.5 g/cm3).

  4. An elementary derivation of the hard/soft-acid/base principle.

    PubMed

    Ayers, Paul W

    2005-04-01

    The hard/soft-acid/base (HSAB) principle indicates that hard acids prefer binding to hard bases (often forming bonds with substantial ionic character) while soft acids prefer binding to soft bases (often forming bonds with substantial covalent character). Though the HSAB principle is a foundational concept of the modern theory of acids and bases, the theoretical underpinnings of the HSAB principle remain murky. This paper examines the exchange reaction, wherein two molecules, one the product of reacting a hard acid and a soft base and the other the product of reacting a soft acid with a hard base, exchange substituents to form the preferred hard-hard and soft-soft product. A simple derivation shows that this reaction is exothermic, proving the validity of the HSAB principle. The analysis leads to the simple and conceptually appealing conclusion that the HSAB principle is a driven by simple electron transfer effects.

  5. ACID-BASE ACCOUNT EFFECTIVENESS FOR DETERMINATION OF MINE WASTE POTENTIAL ACIDITY. (R825549C048)

    EPA Science Inventory

    The oxidation of sulfide minerals in mine waste is a widespread source of resource degradation, often resulting in the generation of acidic water and mobilization of heavy metals. The quantity of acid forming minerals present in mine waste, dominantly as pyrite (FeS2

  6. Design and Characterization of Auxotrophy-Based Amino Acid Biosensors

    PubMed Central

    Bertels, Felix; Merker, Holger; Kost, Christian

    2012-01-01

    Efficient and inexpensive methods are required for the high-throughput quantification of amino acids in physiological fluids or microbial cell cultures. Here we develop an array of Escherichia coli biosensors to sensitively quantify eleven different amino acids. By using online databases, genes involved in amino acid biosynthesis were identified that – upon deletion – should render the corresponding mutant auxotrophic for one particular amino acid. This rational design strategy suggested genes involved in the biosynthesis of arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan, and tyrosine as potential genetic targets. A detailed phenotypic characterization of the corresponding single-gene deletion mutants indeed confirmed that these strains could neither grow on a minimal medium lacking amino acids nor transform any other proteinogenic amino acid into the focal one. Site-specific integration of the egfp gene into the chromosome of each biosensor decreased the detection limit of the GFP-labeled cells by 30% relative to turbidometric measurements. Finally, using the biosensors to determine the amino acid concentration in the supernatants of two amino acid overproducing E. coli strains (i.e. ΔhisL and ΔtdcC) both turbidometrically and via GFP fluorescence emission and comparing the results to conventional HPLC measurements confirmed the utility of the developed biosensor system. Taken together, our study provides not only a genotypically and phenotypically well-characterized set of publicly available amino acid biosensors, but also demonstrates the feasibility of the rational design strategy used. PMID:22829942

  7. Enhanced production of L-sorbose in an industrial Gluconobacter oxydans strain by identification of a strong promoter based on proteomics analysis.

    PubMed

    Hu, Yudong; Wan, Hui; Li, Jianghua; Zhou, Jingwen

    2015-07-01

    Gluconobacter oxydans is capable of rapidly incomplete oxidation of many sugars and alcohols, which means the strain has great potential for industrial purposes. Strong promoters are one of the essential factors that can improve strain performance by overexpression of specific genes. In this study, a pipeline for screening strong promoters by proteomics analysis was established. Based on the procedure, a new strong promoter designated as P B932_2000 was identified in G. oxydans WSH-003. The promoter region was characterized based on known genome sequence information using BPROM. The strength of P B932_2000 was further assessed by analysis of enhanced green fluorescent protein (egfp) expression and comparison with egfp expression by two commonly used strong promoters, P E. coli_tufB and P G. oxydans_tufB . Both quantitative real-time PCR and fluorescence intensities for egfp gene expression showed that P B932_2000 promoter is stronger than the other two. Overexpression of D-sorbitol dehydrogenase (sldh) by P B932_2000 in G. oxydans WSH-003 enhanced the titer and productivity of L-sorbose synthesis from D-sorbitol by 12.0 % and 33.3 %, respectively. These results showed that proteomics analysis is an efficient way to identify strong promoters. The isolated promoter P B932_2000 could further facilitate the metabolic engineering of G. oxydans.

  8. Using problem based learning and guided inquiry in a high school acid-base chemistry unit

    NASA Astrophysics Data System (ADS)

    McKinley, Katie

    The purpose of this investigation was to determine if incorporating problem based learning and guided inquiry would improve student achievement in an acid base unit for high school chemistry. The activities and labs in the unit were modified to be centered around the problem of a fish kill that students investigated. Students also participated in guided inquiry labs to increase the amount of critical thinking and problem solving being done in the classroom. The hypothesis was that the implementation of problem based learning and guided inquiry would foster student learning. Students took a pre-test and post-test on questions covering the objectives of the acid base unit. These assessments were compared to determine the effectiveness of the unit. The results indicate that the unit was effective in increasing student performance on the unit test. This study also analyzed the process of problem based learning. Problem based learning can be an effective method of engaging students in inquiry. However, designing an effective problem based learning unit requires careful design of the problem and enough structure to assure students learn the intended content.

  9. Strong Bilayer Coupling Induced by the Symmetry Breaking in the Monoclinic Phase of BiS2-Based Superconductors

    NASA Astrophysics Data System (ADS)

    Ochi, Masayuki; Akashi, Ryosuke; Kuroki, Kazuhiko

    2016-09-01

    We perform first-principles band structure calculations for the tetragonal and monoclinic structures of LaO0.5F0.5BiS2. We find that the Bi 6px,y bands on two BiS2 layers exhibit a sizable splitting at the X = (π ,0,0) and several other k-points for the monoclinic structure. We show that this feature originates from the inter-BiS2 layer coupling strongly enhanced by the symmetry breaking of the crystal structure. The Fermi surface also shows a large splitting and becomes anisotropic with respect to the kx- and ky-directions in the monoclinic structure, whereas it remains almost flat with respect to the kz-direction.

  10. A theory-based dual-focus alcohol intervention for preadolescents: the Strong African American Families Program.

    PubMed

    Gerrard, Meg; Gibbons, Frederick X; Brody, Gene H; Murry, Velma McBride; Cleveland, Michael J; Wills, Thomas A

    2006-06-01

    This study examined mediators of the Strong African American Families Program, a randomized, dual-focus prevention trial intended to delay the onset of alcohol use and reduce alcohol consumption among rural African American youths. More specifically, it demonstrated that changes in consumption 2 yrs after the intervention were mediated through 2 different paths, a social reaction path and a reasoned/intention path. The social reaction path provided evidence that relative to the control condition, the intervention decreased children's willingness to drink by making their images of drinkers less favorable. The reasoned/intention path provided evidence that the intervention influenced the children's intentions to drink by increasing targeted parenting behaviors related to alcohol. Furthermore, the data demonstrate that these changes in willingness and intentions were independently associated with alcohol consumption at the follow-up, and they suggest that a dual-process model approach that targets both intentions and willingness can be more successful than either approach alone.

  11. Strong domain configuration dependence of the nonlinear dielectric response in (K,Na)NbO{sub 3}-based ceramics

    SciTech Connect

    Huan, Yu; Wang, Xiaohui Li, Longtu; Koruza, Jurij

    2015-11-16

    The nonlinear dielectric response in (Na{sub 0.52}K{sub 0.4425}Li{sub 0.0375})(Nb{sub 0.92−x}Ta{sub x}Sb{sub 0.08})O{sub 3} ceramics with different amounts of Ta was measured using subcoercive electric fields and quantified by the Rayleigh model. The irreversible extrinsic contribution, mainly caused by the irreversible domain wall translation, was strongly dependent on the domain configuration. The irreversible extrinsic contributions remained approximately the same within the single-phase regions, either orthorhombic or tetragonal, due to the similar domain morphology. However, in the polymorphic phase transition region, the domain wall density was increased by minimized domain size, as observed by transmission electron microscopy. This resulted in constrained domain wall motion due to self-clamping and reduced the irreversible extrinsic contribution.

  12. A novel method for estimating the track-soil parameters based on Kalman and improved strong tracking filters.

    PubMed

    Yao, Yu; Cheng, Kai; Zhou, Zhi-Jie; Zhang, Bang-Cheng; Dong, Chao; Zheng, Sen

    2015-11-01

    A tracked vehicle has been widely used in exploring unknown environments and military fields. In current methods for suiting soil conditions, soil parameters need to be given and the traction performance cannot always be satisfied on soft soil. To solve the problem, it is essential to estimate track-soil parameters in real-time. Therefore, a detailed mathematical model is proposed for the first time. Furthermore, a novel algorithm which is composed of Kalman filter (KF) and improved strong tracking filter (STF) is developed for online track-soil estimation and named as KF-ISTF. By this method, the KF is used to estimate slip parameters, and the ISTF is used to estimate motion states. Then the key soil parameters can be estimated by using a suitable soil model. The experimental results show that equipped with the estimation algorithm, the proposed model can be used to estimate the track-soil parameters, and make the traction performance satisfied with soil conditions.

  13. Electroreduction and acid-base properties of dipyrrolylquinoxalines.

    PubMed

    Fu, Zhen; Zhang, Min; Zhu, Weihua; Karnas, Elizabeth; Mase, Kentaro; Ohkubo, Kei; Sessler, Jonathan L; Fukuzumi, Shunichi; Kadish, Karl M

    2012-10-18

    The electroreduction and acid-base properties of dipyrrolylquinoxalines of the form H(2)DPQ, H(2)DPQ(NO(2)), and H(2)DPQ(NO(2))(2) were investigated in benzonitrile (PhCN) containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). This study focuses on elucidating the complete electrochemistry, spectroelectrochemistry, and acid-base properties of H(2)DPQ(NO(2))(n) (n = 0, 1, or 2) in PhCN before and after the addition of trifluoroacetic acid (TFA), tetra-n-butylammonium hydroxide (TBAOH), tetra-n-butylammonium fluoride (TBAF), or tetra-n-butylammonium acetate (TBAOAc) to solution. Electrochemical and spectroelectrochemical data provide support for the formation of a monodeprotonated anion after disproportionation of a dipyrrolylquinoxaline radical anion produced initially. The generated monoanion is then further reduced in two reversible one-electron-transfer steps at more negative potentials in the case of H(2)DPQ(NO(2)) and H(2)DPQ(NO(2))(2). Electrochemically monitored titrations of H(2)DPQ(NO(2))(n) with OH(-), F(-), or OAc(-) (in the form of TBA(+)X(-) salts) give rise to the same monodeprotonated H(2)DPQ(NO(2))(n) produced during electroreduction in PhCN. This latter anion can then be reduced in two additional one-electron-transfer steps in the case of H(2)DPQ(NO(2)) and H(2)DPQ(NO(2))(2). Spectroscopically monitored titrations of H(2)DPQ(NO(2))(n) with X(-) show a 1:2 stoichiometry and provide evidence for the production of both [H(2)DPQ(NO(2))(n)](-) and XHX(-). The spectroscopically measured equilibrium constants range from log β(2) = 5.3 for the reaction of H(2)DPQ with TBAOAc to log β(2) = 8.8 for the reaction of H(2)DPQ(NO(2))(2) with TBAOH. These results are consistent with a combined deprotonation and anion binding process. Equilibrium constants for the addition of one H(+) to each quinoxaline nitrogen of H(2)DPQ, H(2)DPQ(NO(2)), and H(2)DPQ(NO(2))(2) in PhCN containing 0.1 M TBAP were also determined via electrochemical and spectroscopic means

  14. Dengue E Protein Domain III-Based DNA Immunisation Induces Strong Antibody Responses to All Four Viral Serotypes.

    PubMed

    Poggianella, Monica; Slon Campos, José L; Chan, Kuan Rong; Tan, Hwee Cheng; Bestagno, Marco; Ooi, Eng Eong; Burrone, Oscar R

    2015-01-01

    Dengue virus (DENV) infection is a major emerging disease widely distributed throughout the tropical and subtropical regions of the world affecting several millions of people. Despite constants efforts, no specific treatment or effective vaccine is yet available. Here we show a novel design of a DNA immunisation strategy that resulted in the induction of strong antibody responses with high neutralisation titres in mice against all four viral serotypes. The immunogenic molecule is an engineered version of the domain III (DIII) of the virus E protein fused to the dimerising CH3 domain of the IgG immunoglobulin H chain. The DIII sequences were also codon-optimised for expression in mammalian cells. While DIII alone is very poorly secreted, the codon-optimised fusion protein is rightly expressed, folded and secreted at high levels, thus inducing strong antibody responses. Mice were immunised using gene-gun technology, an efficient way of intradermal delivery of the plasmid DNA, and the vaccine was able to induce neutralising titres against all serotypes. Additionally, all sera showed reactivity to a recombinant DIII version and the recombinant E protein produced and secreted from mammalian cells in a mono-biotinylated form when tested in a conformational ELISA. Sera were also highly reactive to infective viral particles in a virus-capture ELISA and specific for each serotype as revealed by the low cross-reactive and cross-neutralising activities. The serotype specific sera did not induce antibody dependent enhancement of infection (ADE) in non-homologous virus serotypes. A tetravalent immunisation protocol in mice showed induction of neutralising antibodies against all four dengue serotypes as well.

  15. Dengue E Protein Domain III-Based DNA Immunisation Induces Strong Antibody Responses to All Four Viral Serotypes

    PubMed Central

    Chan, Kuan Rong; Tan, Hwee Cheng; Bestagno, Marco; Ooi, Eng Eong; Burrone, Oscar R.

    2015-01-01

    Dengue virus (DENV) infection is a major emerging disease widely distributed throughout the tropical and subtropical regions of the world affecting several millions of people. Despite constants efforts, no specific treatment or effective vaccine is yet available. Here we show a novel design of a DNA immunisation strategy that resulted in the induction of strong antibody responses with high neutralisation titres in mice against all four viral serotypes. The immunogenic molecule is an engineered version of the domain III (DIII) of the virus E protein fused to the dimerising CH3 domain of the IgG immunoglobulin H chain. The DIII sequences were also codon-optimised for expression in mammalian cells. While DIII alone is very poorly secreted, the codon-optimised fusion protein is rightly expressed, folded and secreted at high levels, thus inducing strong antibody responses. Mice were immunised using gene-gun technology, an efficient way of intradermal delivery of the plasmid DNA, and the vaccine was able to induce neutralising titres against all serotypes. Additionally, all sera showed reactivity to a recombinant DIII version and the recombinant E protein produced and secreted from mammalian cells in a mono-biotinylated form when tested in a conformational ELISA. Sera were also highly reactive to infective viral particles in a virus-capture ELISA and specific for each serotype as revealed by the low cross-reactive and cross-neutralising activities. The serotype specific sera did not induce antibody dependent enhancement of infection (ADE) in non-homologous virus serotypes. A tetravalent immunisation protocol in mice showed induction of neutralising antibodies against all four dengue serotypes as well. PMID:26218926

  16. Microwave-assisted acid and base hydrolysis of intact proteins containing disulfide bonds for protein sequence analysis by mass spectrometry.

    PubMed

    Reiz, Bela; Li, Liang

    2010-09-01

    Controlled hydrolysis of proteins to generate peptide ladders combined with mass spectrometric analysis of the resultant peptides can be used for protein sequencing. In this paper, two methods of improving the microwave-assisted protein hydrolysis process are described to enable rapid sequencing of proteins containing disulfide bonds and increase sequence coverage, respectively. It was demonstrated that proteins containing disulfide bonds could be sequenced by MS analysis by first performing hydrolysis for less than 2 min, followed by 1 h of reduction to release the peptides originally linked by disulfide bonds. It was shown that a strong base could be used as a catalyst for microwave-assisted protein hydrolysis, producing complementary sequence information to that generated by microwave-assisted acid hydrolysis. However, using either acid or base hydrolysis, amide bond breakages in small regions of the polypeptide chains of the model proteins (e.g., cytochrome c and lysozyme) were not detected. Dynamic light scattering measurement of the proteins solubilized in an acid or base indicated that protein-protein interaction or aggregation was not the cause of the failure to hydrolyze certain amide bonds. It was speculated that there were some unknown local structures that might play a role in preventing an acid or base from reacting with the peptide bonds therein.

  17. A Comparison of Different Teaching Designs of "Acids and Bases" Subject

    ERIC Educational Resources Information Center

    Ültay, Neslihan; Çalik, Muammer

    2016-01-01

    Inability to link the acid-base concepts with daily life phenomena (as contexts) highlights the need for further research on the context-based acid-base chemistry. In this vein, the aim of this study is to investigate the effects of different teaching designs (REACT strategy, 5Es learning model and traditional (existing) instruction) relevant with…

  18. Hands-On Science: Is It an Acid or a Base? These Colorful Tests Tell All!

    ERIC Educational Resources Information Center

    VanCleave, Janice

    1998-01-01

    Two hands-on science activities for K-6 students teach them how to determine if something is an acid or a base. The activities require acid/base indicator juice, testing strips, and a base solution. A recipe for making them in the classroom using red cabbage and baking soda is provided. (SM)

  19. A new oxidimetric reagent: potassium dichromate in a strong phosphoric acid medium-VI Potentiometric titration of vanadium(III) alone and in mixture with vanadium(IV).

    PubMed

    Rao, G G; Rao, P K

    1966-09-01

    Vanadium(III) can be titrated at room temperature with potassium dichromate in an 8-12M phosphoric acid medium. Two potential breaks are observed in 12M phosphoric add with 0.2N potassium dichromate, the first corresponding to the oxidation of vanadium(III) to vanadium(IV) and the second to the oxidation of vanadium(IV) to vanadium(V). In titrations with 0.05N dichromate only the first break in potential is clearly observed. The method has been extended to the titration of mixtures of vanadium(III) and vanadium(IV). Conditions have also been found for the visual titration of vanadium(III) using ferroln or barium diphenylamine sulphonate as indicator.

  20. 77 FR 16126 - Microbiology Devices; Reclassification of Nucleic Acid-Based Systems for Mycobacterium tuberculosis

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-19

    ... Food and Drug Administration 21 CFR Part 866 Microbiology Devices; Reclassification of Nucleic Acid...: Proposed rule. SUMMARY: The Food and Drug Administration (FDA) is proposing to reclassify nucleic acid... effectiveness of the device for its intended use. II. Regulatory Background of the Device Nucleic acid-based...