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Sample records for acid base chemistry

  1. 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.

  2. 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…

  3. 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…

  4. 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…

  5. 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".

  6. How Do Undergraduate Students Conceptualize Acid-Base Chemistry? Measurement of a Concept Progression

    ERIC Educational Resources Information Center

    Romine, William L.; Todd, Amber N.; Clark, Travis B.

    2016-01-01

    We developed and validated a new instrument, called "Measuring Concept progressions in Acid-Base chemistry" (MCAB) and used it to better understand the progression of undergraduate students' understandings about acid-base chemistry. Items were developed based on an existing learning progression for acid-base chemistry. We used the Rasch…

  7. 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.

  8. Canonical Pedagogical Content Knowledge by Cores for Teaching Acid-Base Chemistry at High School

    ERIC Educational Resources Information Center

    Alvarado, Clara; Cañada, Florentina; Garritz, Andoni; Mellado, Vicente

    2015-01-01

    The topic of acid-base chemistry is one of the oldest in general chemistry courses and it has been almost continuously in academic discussion. The central purpose of documenting the knowledge and beliefs of a group of ten Mexican teachers with experience in teaching acid-base chemistry in high school was to know how they design, prepare and…

  9. Improving pharmacy students' understanding and long-term retention of acid-base chemistry.

    PubMed

    Roche, Victoria F

    2007-12-15

    Despite repeated exposure to the principles underlying the behavior of organic acids and bases in aqueous solution, some pharmacy students remain confused about the topic of acid-base chemistry. Since a majority of organic drug molecules have acid-base character, the ability to predict their reactivity and the extent to which they will ionize in a given medium is paramount to students' understanding of essentially all aspects of drug action in vivo and in vitro. This manuscript presents a medicinal chemistry lesson in the fundamentals of acid-base chemistry that many pharmacy students have found enlightening and clarifying.

  10. Improving Pharmacy Students' Understanding and Long-term Retention of Acid-Base Chemistry

    PubMed Central

    2007-01-01

    Despite repeated exposure to the principles underlying the behavior of organic acids and bases in aqueous solution, some pharmacy students remain confused about the topic of acid-base chemistry. Since a majority of organic drug molecules have acid-base character, the ability to predict their reactivity and the extent to which they will ionize in a given medium is paramount to students' understanding of essentially all aspects of drug action in vivo and in vitro. This manuscript presents a medicinal chemistry lesson in the fundamentals of acid-base chemistry that many pharmacy students have found enlightening and clarifying PMID:19503706

  11. Experienced Teachers' Pedagogical Content Knowledge of Teaching Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Drechsler, Michal; Van Driel, Jan

    2008-01-01

    We investigated the pedagogical content knowledge (PCK) of nine experienced chemistry teachers. The teachers took part in a teacher training course on students' difficulties and the use of models in teaching acid-base chemistry, electrochemistry, and redox reactions. Two years after the course, the teachers were interviewed about their PCK of (1)…

  12. Thai Grade 11 Students' Alternative Conceptions for Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Artdej, Romklao; Ratanaroutai, Thasaneeya; Coll, Richard Kevin; Thongpanchang, Tienthong

    2010-01-01

    This study involved the development of a two-tier diagnostic instrument to assess Thai high school students' understanding of acid-base chemistry. The acid-base diagnostic test (ABDT) comprising 18 items was administered to 55 Grade 11 students in a science and mathematics programme during the second semester of the 2008 academic year. Analysis of…

  13. Examining the Mismatch between Pupil and Teacher Knowledge in Acid-Base Chemistry.

    ERIC Educational Resources Information Center

    Erduran, Sibel

    2003-01-01

    Reports a mismatch between teacher and pupil knowledge of acid-base chemistry as a result of controversial episodes from three science lessons. Suggests that the teacher's knowledge is guided by textbook information while the pupil's knowledge is based on direct experimental experience. Proposes that classroom activities should support the…

  14. General Chemistry Students' Conceptual Understanding and Language Fluency: Acid-Base Neutralization and Conductometry

    ERIC Educational Resources Information Center

    Nyachwaya, James M.

    2016-01-01

    The objective of this study was to examine college general chemistry students' conceptual understanding and language fluency in the context of the topic of acids and bases. 115 students worked in groups of 2-4 to complete an activity on conductometry, where they were given a scenario in which a titration of sodium hydroxide solution and dilute…

  15. Equilibrium II: Acids and Bases. Independent Learning Project for Advanced Chemistry (ILPAC). Unit P3.

    ERIC Educational Resources Information Center

    Inner London Education Authority (England).

    This unit on equilibrium is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, which consists of two levels, focuses on the application of equilibrium principles to equilibria involving weak acids and bases, including buffer solutions and indicators. Level one uses Le Chatelier's…

  16. Conceptual Understanding of Acids and Bases Concepts and Motivation to Learn Chemistry

    ERIC Educational Resources Information Center

    Cetin-Dindar, Ayla; Geban, Omer

    2017-01-01

    The purpose of this study was to investigate the effect of 5E learning cycle model oriented instruction (LCMI) on 11th-grade students' conceptual understanding of acids and bases concepts and student motivation to learn chemistry. The study, which lasted for 7 weeks, involved two groups: An experimental group (LCMI) and a control group (the…

  17. Acid-Base Learning Outcomes for Students in an Introductory Organic Chemistry Course

    ERIC Educational Resources Information Center

    Stoyanovich, Carlee; Gandhi, Aneri; Flynn, Alison B.

    2015-01-01

    An outcome-based approach to teaching and learning focuses on what the student demonstrably knows and can do after instruction, rather than on what the instructor teaches. This outcome-focused approach can then guide the alignment of teaching strategies, learning activities, and assessment. In organic chemistry, mastery of organic acid-base…

  18. 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.

  19. How are the Concepts and Theories of Acid-Base Reactions Presented? Chemistry in Textbooks and as Presented by Teachers

    ERIC Educational Resources Information Center

    Furio-Mas, Carlos; Calatayud, Maria Luisa; Guisasola, Jenaro; Furio-Gomez, Cristina

    2005-01-01

    This paper investigates the views of science and scientific activity that can be found in chemistry textbooks and heard from teachers when acid-base reactions are introduced to grade 12 and university chemistry students. First, the main macroscopic and microscopic conceptual models are developed. Second, we attempt to show how the existence of…

  20. STREAMWATER ACID-BASED CHEMISTRY AND CRITICAL LOADS OF ATMOSPHERIC SULFUR DEPOSITION IN SHENANDOAH NATIONAL PARK, VIRGINIA

    EPA Science Inventory

    A modeling study was conducted to evaluate the acid-base chemistry of streams within Shenandoah National Park, Virginia and to project future responses to sulfur (S) and nitrogen (N) atmospheric emissions controls. Many of the major stream systems in the Park have acid neutraliz...

  1. On the Prevalence of Alternative Conceptions on Acid-Base Chemistry among Secondary Students: Insights from Cognitive and Confidence Measures

    ERIC Educational Resources Information Center

    Hoe, Kai Yee; Subramaniam, R.

    2016-01-01

    This study presents an analysis of alternative conceptions (ACs) on acid--base chemistry harbored by grade 9 students in Singapore. The ACs were obtained by the development and validation of a 4-tier diagnostic instrument. It is among the very few studies in the science education literature that have focused on examining results based also on…

  2. Unravelling the surface chemistry of metal oxide nanocrystals, the role of acids and bases.

    PubMed

    De Roo, Jonathan; Van den Broeck, Freya; De Keukeleere, Katrien; Martins, José C; Van Driessche, Isabel; Hens, Zeger

    2014-07-09

    We synthesized HfO2 nanocrystals from HfCl4 using a surfactant-free solvothermal process in benzyl alcohol and found that the resulting nanocrystals could be transferred to nonpolar media using a mixture of carboxylic acids and amines. Using solution (1)H NMR, FTIR, and elemental analysis, we studied the details of the transfer reaction and the surface chemistry of the resulting sterically stabilized nanocrystals. As-synthesized nanocrystals are charge-stabilized by protons, with chloride acting as the counterion. Treatment with only carboxylic acids does not lead to any binding of ligands to the HfO2 surface. On the other hand, we find that the addition of amines provides the basic environment in which carboxylic acids can dissociate and replace chloride. This results in stable, aggregate-free dispersions of HfO2 nanocrystals, sterically stabilized by carboxylate ligands. Moreover, titrations with deuterated carboxylic acid show that the charge on the carboxylate ligands is balanced by coadsorbed protons. Hence, opposite from the X-type/nonstoichiometric nanocrystals picture prevailing in literature, one should look at HfO2/carboxylate nanocrystals as systems where carboxylic acids are dissociatively adsorbed to bind to the nanocrystals. Similar results were obtained with ZrO2 NCs. Since proton accommodation on the surface is most likely due to the high Brønsted basicity of oxygen, our model could be a more general picture for the surface chemistry of metal oxide nanocrystals with important consequences on the chemistry of ligand exchange reactions.

  3. College Chemistry Students' Mental Models of Acids and Acid Strength

    ERIC Educational Resources Information Center

    McClary, LaKeisha; Talanquer, Vicente

    2011-01-01

    The central goal of this study was to characterize the mental models of acids and acid strength expressed by advanced college chemistry students when engaged in prediction, explanation, and justification tasks that asked them to rank chemical compounds based on their relative acid strength. For that purpose we completed a qualitative research…

  4. Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries.

    PubMed

    Prentice, Boone M; McLuckey, Scott A

    2013-02-01

    Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field.

  5. Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries

    PubMed Central

    Prentice, Boone M.

    2013-01-01

    Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field. PMID:23257901

  6. Lewis Acid-Base, Molecular Modeling, and Isotopic Labeling in a Sophomore Inorganic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nataro, Chip; Ferguson, Michelle A.; Bocage, Katherine M.; Hess, Brian J.; Ross, Vincent J.; Swarr, Daniel T.

    2004-01-01

    An experiment to prepare a deuterium labeled adduct of a Lewis acid and Lewis base, to use computational methods allowing students to visualize the LUMO of Lewis acids, the HOMO of Lewis bases and the molecular orbitals of the adduct that is formed is developed. This allows students to see the interplay between calculated and experimental results.

  7. 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

  8. 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.

  9. Chemistry of ascorbic acid radicals

    SciTech Connect

    Bielski, B.H.J.

    1982-01-01

    The chemistry of ascorbic acid free radicals is reviewed. Particular emphasis is placed on identification and characterization of ascorbate radicals by spectrophotometric and electron paramagnetic resonance techniques, the kinetics of formation and disappearance of ascorbate free radicals in enzymatic and nonenzymatic reactions, the effect of pH upon the spectral and kinetic properties of ascorbate anion radical, and chemical reactivity of ascorbate free radicals.

  10. 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

  11. tRNA acceptor-stem and anticodon bases embed separate features of amino acid chemistry

    PubMed Central

    Carter, Charles W.; Wolfenden, Richard

    2016-01-01

    abstract The universal genetic code is a translation table by which nucleic acid sequences can be interpreted as polypeptides with a wide range of biological functions. That information is used by aminoacyl-tRNA synthetases to translate the code. Moreover, amino acid properties dictate protein folding. We recently reported that digital correlation techniques could identify patterns in tRNA identity elements that govern recognition by synthetases. Our analysis, and the functionality of truncated synthetases that cannot recognize the tRNA anticodon, support the conclusion that the tRNA acceptor stem houses an independent code for the same 20 amino acids that likely functioned earlier in the emergence of genetics. The acceptor-stem code, related to amino acid size, is distinct from a code in the anticodon that is related to amino acid polarity. Details of the acceptor-stem code suggest that it was useful in preserving key properties of stereochemically-encoded peptides that had developed the capacity to interact catalytically with RNA. The quantitative embedding of the chemical properties of amino acids into tRNA bases has implications for the origins of molecular biology. PMID:26595350

  12. Acid-Base Chemistry According to Robert Boyle: Chemical Reactions in Words as well as Symbols

    ERIC Educational Resources Information Center

    Goodney, David E.

    2006-01-01

    Examples of acid-base reactions from Robert Boyle's "The Sceptical Chemist" are used to illustrate the rich information content of chemical equations. Boyle required lengthy passages of florid language to describe the same reaction that can be done quite simply with a chemical equation. Reading or hearing the words, however, enriches the student's…

  13. A Prebiotic Chemistry Experiment on the Adsorption of Nucleic Acids Bases onto a Natural Zeolite

    NASA Astrophysics Data System (ADS)

    Anizelli, Pedro R.; Baú, João Paulo T.; Gomes, Frederico P.; da Costa, Antonio Carlos S.; Carneiro, Cristine E. A.; Zaia, Cássia Thaïs B. V.; Zaia, Dimas A. M.

    2015-09-01

    There are currently few mechanisms that can explain how nucleic acid bases were synthesized, concentrated from dilute solutions, and/or protected against degradation by UV radiation or hydrolysis on the prebiotic Earth. A natural zeolite exhibited the potential to adsorb adenine, cytosine, thymine, and uracil over a range of pH, with greater adsorption of adenine and cytosine at acidic pH. Adsorption of all nucleic acid bases was decreased in artificial seawater compared to water, likely due to cation complexation. Furthermore, adsorption of adenine appeared to protect natural zeolite from thermal degradation. The C=O groups from thymine, cytosine and uracil appeared to assist the dissolution of the mineral while the NH2 group from adenine had no effect. As shown by FT-IR spectroscopy, adenine interacted with a natural zeolite through the NH2 group, and cytosine through the C=O group. A pseudo-second-order model best described the kinetics of adenine adsorption, which occurred faster in artificial seawaters.

  14. A Prebiotic Chemistry Experiment on the Adsorption of Nucleic Acids Bases onto a Natural Zeolite.

    PubMed

    Anizelli, Pedro R; Baú, João Paulo T; Gomes, Frederico P; da Costa, Antonio Carlos S; Carneiro, Cristine E A; Zaia, Cássia Thaïs B V; Zaia, Dimas A M

    2015-09-01

    There are currently few mechanisms that can explain how nucleic acid bases were synthesized, concentrated from dilute solutions, and/or protected against degradation by UV radiation or hydrolysis on the prebiotic Earth. A natural zeolite exhibited the potential to adsorb adenine, cytosine, thymine, and uracil over a range of pH, with greater adsorption of adenine and cytosine at acidic pH. Adsorption of all nucleic acid bases was decreased in artificial seawater compared to water, likely due to cation complexation. Furthermore, adsorption of adenine appeared to protect natural zeolite from thermal degradation. The C=O groups from thymine, cytosine and uracil appeared to assist the dissolution of the mineral while the NH2 group from adenine had no effect. As shown by FT-IR spectroscopy, adenine interacted with a natural zeolite through the NH2 group, and cytosine through the C=O group. A pseudo-second-order model best described the kinetics of adenine adsorption, which occurred faster in artificial seawaters.

  15. Interactions between groundwater and surface water in a Virginia coastal plain watershed. 2. Acid-base chemistry

    USGS Publications Warehouse

    O'Brien, A. K.; Eshleman, K.N.; Pollard, J.S.

    1994-01-01

    At the Reedy Creek watershed sulphate concentrations were higher and alkalinity lower in the groundwater in the hillslope than in the stream. Sulphate concentrations and alkalinity observed in groundwater in the wetland were usually between those of the hillslope and stream. These data suggest that the wetland is a sink for sulphate and acidity; sulphate reduction may be an important mechanism for generating alkalinity in the wetland. The DOC concentrations were higher in the stream and wetland groundwater than in hillslope groundwater. No consistent spatial patterns in sulphate concentrations were observed in surface water chemistry under base flow conditions. Stream discharge was found to be positively correlated with base flow sulphate concentrations and inversely correlated with alkalinity. A sulphate mass balance indicated that approximately 30% of the estimated 24.9 kg SO42-/ha yr wet atmospheric input was exported from the watershed as sulphate in stream runoff in the water year 1990. -from Authors

  16. The effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid/base chemistry: Implications for Eocene and Cretaceous ocean carbon chemistry and buffering

    NASA Astrophysics Data System (ADS)

    Hain, Mathis P.; Sigman, Daniel M.; Higgins, John A.; Haug, Gerald H.

    2015-05-01

    Reconstructed changes in seawater calcium and magnesium concentration ([Ca2+], [Mg2+]) predictably affect the ocean's acid/base and carbon chemistry. Yet inaccurate formulations of chemical equilibrium "constants" are currently in use to account for these changes. Here we develop an efficient implementation of the MIAMI Ionic Interaction Model to predict all chemical equilibrium constants required for carbon chemistry calculations under variable [Ca2+] and [Mg2+]. We investigate the impact of [Ca2+] and [Mg2+] on the relationships among the ocean's pH, CO2, dissolved inorganic carbon (DIC), saturation state of CaCO3 (Ω), and buffer capacity. Increasing [Ca2+] and/or [Mg2+] enhances "ion pairing," which increases seawater buffering by increasing the concentration ratio of total to "free" (uncomplexed) carbonate ion. An increase in [Ca2+], however, also causes a decline in carbonate ion to maintain a given Ω, thereby overwhelming the ion pairing effect and decreasing seawater buffering. Given the reconstructions of Eocene [Ca2+] and [Mg2+] ([Ca2+]~20 mM; [Mg2+]~30 mM), Eocene seawater would have required essentially the same DIC as today to simultaneously explain a similar-to-modern Ω and the estimated Eocene atmospheric CO2 of ~1000 ppm. During the Cretaceous, at ~4 times modern [Ca2+], ocean buffering would have been at a minimum. Overall, during times of high seawater [Ca2+], CaCO3 saturation, pH, and atmospheric CO2 were more susceptible to perturbations of the global carbon cycle. For example, given both Eocene and Cretaceous seawater [Ca2+] and [Mg2+], a doubling of atmospheric CO2 would require less carbon addition to the ocean/atmosphere system than under modern seawater composition. Moreover, increasing seawater buffering since the Cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and CO2 concentration mechanisms that aid photosynthesis.

  17. "Click" Chemistry-Tethered Hyaluronic Acid-Based Contact Lens Coatings Improve Lens Wettability and Lower Protein Adsorption.

    PubMed

    Deng, Xudong; Korogiannaki, Myrto; Rastegari, Banafsheh; Zhang, Jianfeng; Chen, Mengsu; Fu, Qiang; Sheardown, Heather; Filipe, Carlos D M; Hoare, Todd

    2016-08-31

    Improving the wettability of and reducing the protein adsorption to contact lenses may be beneficial for improving wearer comfort. Herein, we describe a simple "click" chemistry approach to surface functionalize poly(2-hydroxyethyl methacrylate) (pHEMA)-based contact lenses with hyaluronic acid (HA), a carbohydrate naturally contributing to the wettability of the native tear film. A two-step preparation technique consisting of laccase/TEMPO-mediated oxidation followed by covalent grafting of hydrazide-functionalized HA via simple immersion resulted in a model lens surface that is significantly more wettable, more water retentive, and less protein binding than unmodified pHEMA while maintaining the favorable transparency, refractive, and mechanical properties of a native lens. The dipping/coating method we developed to covalently tether the HA wetting agent is simple, readily scalable, and a highly efficient route for contact lens modification.

  18. Chemical Equilibrium, Unit 4: Equilibria in Acid-Base Systems. A Computer-Enriched Module for Introductory Chemistry. Student's Guide and Teacher's Guide.

    ERIC Educational Resources Information Center

    Settle, Frank A., Jr.

    Presented are the teacher's guide and student materials for one of a series of self-instructional, computer-based learning modules for an introductory, undergraduate chemistry course. The student manual for this acid-base equilibria unit includes objectives, prerequisites, pretest, a discussion of equilibrium constants, and 20 problem sets.…

  19. A Comparative Study of the Effects of a Concept Mapping Enhanced Laboratory Experience on Turkish High School Students' Understanding of Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Ozmen, Haluk; Demircioglu, Gokhan; Coll, Richard K.

    2009-01-01

    The research reported here consists of the introduction of an intervention based on a series of laboratory activities combined with concept mapping. The purpose of this intervention was to enhance student understanding of acid-base chemistry for tenth grade students' from two classes in a Turkish high school. An additional aim was to enhance…

  20. "JCE" Classroom Activity #110: Artistic Anthocyanins and Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Lech, Jenna; Dounin, Vladimir

    2011-01-01

    Art and science are sometimes viewed as opposing subjects, but are united in many ways. With an increased awareness of the benefits of interdisciplinary studies in education, it is desirable to show students how different subjects impact one another. Visual arts are greatly connected to chemistry in several ways. Pigments are usually synthetically…

  1. Dynamic Covalent Chemistry-based Sensing: Pyrenyl Derivatives of Phenylboronic Acid for Saccharide and Formaldehyde

    NASA Astrophysics Data System (ADS)

    Chang, Xingmao; Fan, Jiayun; Wang, Min; Wang, Zhaolong; Peng, Haonan; He, Gang; Fang, Yu

    2016-08-01

    We synthesized two specially designed pyrenyl (Py) derivatives of phenylboronic acid, PSNB1 and PSNB2, of which PSNB2 self-assemble to form dynamic aggregate in methanol-water mixture (1:99, v/v) via intermolecular H-bonding and pi-pi stacking. Interestingly, the dynamic aggregate shows smart response to presence of fructose (F) as evidenced by fluorescence color change from green to blue. More interestingly, the fluorescence emission of the resulted PSNB2-F changes from blue to green with the addition of formaldehyde (FA). The reason behind is formation of a PSNB2-F dimer via FA cross-linking. Based upon the reactions as found, sensitive and fast sensing of F and FA in water was realized, of which the experimental DLs could be significantly lower than 10 μM for both analytes, and the response times are less than 1 min. It is believed that not only the materials as created may have the potential to find real-life applications but also the strategy as developed can be adopted to develop other dynamic materials.

  2. Dynamic Covalent Chemistry-based Sensing: Pyrenyl Derivatives of Phenylboronic Acid for Saccharide and Formaldehyde

    PubMed Central

    Chang, Xingmao; Fan, Jiayun; Wang, Min; Wang, Zhaolong; Peng, Haonan; He, Gang; Fang, Yu

    2016-01-01

    We synthesized two specially designed pyrenyl (Py) derivatives of phenylboronic acid, PSNB1 and PSNB2, of which PSNB2 self-assemble to form dynamic aggregate in methanol-water mixture (1:99, v/v) via intermolecular H-bonding and pi-pi stacking. Interestingly, the dynamic aggregate shows smart response to presence of fructose (F) as evidenced by fluorescence color change from green to blue. More interestingly, the fluorescence emission of the resulted PSNB2-F changes from blue to green with the addition of formaldehyde (FA). The reason behind is formation of a PSNB2-F dimer via FA cross-linking. Based upon the reactions as found, sensitive and fast sensing of F and FA in water was realized, of which the experimental DLs could be significantly lower than 10 μM for both analytes, and the response times are less than 1 min. It is believed that not only the materials as created may have the potential to find real-life applications but also the strategy as developed can be adopted to develop other dynamic materials. PMID:27498703

  3. Promoting Student Development of Models and Scientific Inquiry Skills in Acid-Base Chemistry: An Important Skill Development in Preparation for AP Chemistry

    ERIC Educational Resources Information Center

    Hale-Hanes, Cara

    2015-01-01

    In this study, two groups of 11th grade chemistry students (n = 210) performed a sequence of hands-on and virtual laboratories that were progressively more inquiry-based. One-half of the students did the laboratory sequence with the addition of a teacher-led discussion connecting student data to student-generated visual representations of…

  4. What are they thinking? Automated analysis of student writing about acid-base chemistry in introductory biology.

    PubMed

    Haudek, Kevin C; Prevost, Luanna B; Moscarella, Rosa A; Merrill, John; Urban-Lurain, Mark

    2012-01-01

    Students' writing can provide better insight into their thinking than can multiple-choice questions. However, resource constraints often prevent faculty from using writing assessments in large undergraduate science courses. We investigated the use of computer software to analyze student writing and to uncover student ideas about chemistry in an introductory biology course. Students were asked to predict acid-base behavior of biological functional groups and to explain their answers. Student explanations were rated by two independent raters. Responses were also analyzed using SPSS Text Analysis for Surveys and a custom library of science-related terms and lexical categories relevant to the assessment item. These analyses revealed conceptual connections made by students, student difficulties explaining these topics, and the heterogeneity of student ideas. We validated the lexical analysis by correlating student interviews with the lexical analysis. We used discriminant analysis to create classification functions that identified seven key lexical categories that predict expert scoring (interrater reliability with experts = 0.899). This study suggests that computerized lexical analysis may be useful for automatically categorizing large numbers of student open-ended responses. Lexical analysis provides instructors unique insights into student thinking and a whole-class perspective that are difficult to obtain from multiple-choice questions or reading individual responses.

  5. A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus

    NASA Astrophysics Data System (ADS)

    Vet, Robert; Artz, Richard S.; Carou, Silvina

    2014-08-01

    Investigating and assessing the chemical composition of precipitation and atmospheric deposition is essential to understanding how atmospheric pollutants contribute to contemporary environmental concerns including ecosystem acidification and eutrophication, loss of biodiversity, air pollution and global climate change. Evidence of the link between atmospheric deposition and these environmental issues is well established. The state of scientific understanding of this link is that present levels of atmospheric deposition of sulfur and nitrogen adversely affect terrestrial and aquatic ecosystems, putting forest sustainability and aquatic biodiversity at risk. Nitrogen and phosphorus loadings are linked to impacts on the diversity of terrestrial and aquatic vegetation through biological cycling, and atmospheric deposition plays a major role in the emission-transport-conversion-loss cycle of chemicals in the atmosphere as well as the formation of particulate matter and ozone in the troposphere. Evidence also shows that atmospheric constituents are changing the earth's climate through direct and indirect atmospheric processes. This Special Issue, comprising a single article titled "A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus", presents a recent comprehensive review of precipitation chemistry and atmospheric deposition at global and regional scales. The information in the Special Issue, including all supporting data sets and maps, is anticipated to be of great value not only to the atmospheric deposition community but also to other science communities including those that study ecosystem impacts, human health effects, nutrient processing, climate change, global and hemispheric modeling and biogeochemical cycling. Understanding and quantifying pollutant loss from the atmosphere is, and will remain, an important component of each of these scientific fields as they

  6. The development of learning media of acid-base indicator from extract of natural colorant as an alternative media in learning chemistry

    NASA Astrophysics Data System (ADS)

    Nurhadi, Mukhamad; Wirhanuddin, Erwin, Muflihah, Erika, Farah; Widiyowati, Iis Intan

    2017-03-01

    The development of learning media of acid base indicator from extract of natural colorants as an alternative media in chemistry learning; acid-base solution by using creative problem solving model at SMA N 10 Samarinda has been done. This research aimed to create and develop the learning media from extract of natural colorants, measure its quality and effectiveness, and measure the quality of student learning outcome in acid-base solution topic by using that media. The development process used Analysis, Design, Development, Implementation, and Evaluation (ADDIE) method. The learning media of acid-base indicator was created in the form of box experiment. Its quality was in the range of very good and it was effectively applied in the learning and gave positive impact on the achievement of learning goals.

  7. Identification of Weak Acids and Bases by Titration with Primary Standards. A Modern Version of an Old Analytical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Thompson, Robert Q.

    1988-01-01

    Describes a laboratory exercise in which acid dissociation constants and molecular weights are extracted from sample data and the sample is identified. Emphasizes accurate volumetric work while bringing to practice the concepts of acid-base equilibria, activity coefficients, and thermodynamic constants. (CW)

  8. Assessing Changes in High School Students' Conceptual Understanding through Concept Maps before and after the Computer-Based Predict-Observe-Explain (CB-POE) Tasks on Acid-Base Chemistry at the Secondary Level

    ERIC Educational Resources Information Center

    Yaman, Fatma; Ayas, Alipasa

    2015-01-01

    Although concept maps have been used as alternative assessment methods in education, there has been an ongoing debate on how to evaluate students' concept maps. This study discusses how to evaluate students' concept maps as an assessment tool before and after 15 computer-based Predict-Observe-Explain (CB-POE) tasks related to acid-base chemistry.…

  9. Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

    2013-01-01

    A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

  10. Investigation of acid-base catalysis in the extradiol and intradiol catechol dioxygenase reactions using a broad specificity mutant enzyme and model chemistry.

    PubMed

    Brivio, Michela; Schlosrich, Janne; Ahmad, Mark; Tolond, Caroline; Bugg, Timothy D H

    2009-04-07

    The extradiol and intradiol catechol dioxygenase reaction mechanisms proceed via a common proximal hydroperoxide intermediate, which is processed via different Criegee 1,2-rearrangements. An R215W mutant of extradiol dioxygenase MhpB, able to produce a mixture of extradiol and intradiol cleavage products, was analysed at pH 5.2-8.6, and the yield of extradiol product was found to be highly pH-dependent, whereas the yield of intradiol product was pH-independent. The acid-base chemistry of a biomimetic reaction for extradiol oxidative catechol cleavage was also investigated, using 1,4,7-triazacyclononane, FeCl(2), and pyridine in methanol, in which pyridine is proposed to act as both a general base and (in protonated form) a general acid. Kinetic experiments using a range of meta- and para-substituted pyridines gave a Brønsted plot of log(v) vs. pK(a) showing a bell-shaped plot. Oxidative catechol cleavage by a pyridine-monosubstituted beta-cyclodextrin in the presence of TACN and FeCl(2) in methanol yielded only intradiol cleavage products. It is therefore proposed that bifunctional acid-base catalysis is required for iron (ii)-dependent extradiol catechol cleavage, whereas the rate-determining step for intradiol catechol cleavage does not involve acid-base catalysis.

  11. Advances in the biology and chemistry of sialic acids.

    PubMed

    Chen, Xi; Varki, Ajit

    2010-02-19

    Sialic acids are a subset of nonulosonic acids, which are nine-carbon alpha-keto aldonic acids. Natural existing sialic acid-containing structures are presented in different sialic acid forms, various sialyl linkages, and on diverse underlying glycans. They play important roles in biological, pathological, and immunological processes. Sialobiology has been a challenging and yet attractive research area. Recent advances in chemical and chemoenzymatic synthesis, as well as large-scale E. coli cell-based production, have provided a large library of sialoside standards and derivatives in amounts sufficient for structure-activity relationship studies. Sialoglycan microarrays provide an efficient platform for quick identification of preferred ligands for sialic acid-binding proteins. Future research on sialic acid will continue to be at the interface of chemistry and biology. Research efforts not only will lead to a better understanding of the biological and pathological importance of sialic acids and their diversity but also could lead to the development of therapeutics.

  12. The Role of Green Chemistry Activities in Fostering Secondary School Students' Understanding of Acid-Base Concepts and Argumentation Skills

    ERIC Educational Resources Information Center

    Karpudewan, Mageswary; Roth, Wolff Michael; Sinniah, Devananthini

    2016-01-01

    In a world where environmental degradation is taking on alarming levels, understanding, and acting to minimize, the individual environmental impact is an important goal for many science educators. In this study, a green chemistry curriculum--combining chemistry experiments with everyday, environmentally friendly substances with a student-centered…

  13. Sulfenic acid chemistry, detection and cellular lifetime☆

    PubMed Central

    Gupta, Vinayak; Carroll, Kate S.

    2014-01-01

    Background Reactive oxygen species-mediated cysteine sulfenic acid modification has emerged as an important regulatory mechanism in cell signaling. The stability of sulfenic acid in proteins is dictated by the local microenvironment and ability of antioxidants to reduce this modification. Several techniques for detecting this cysteine modification have been developed, including direct and in situ methods. Scope of review This review presents a historical discussion of sulfenic acid chemistry and highlights key examples of this modification in proteins. A comprehensive survey of available detection techniques with advantages and limitations is discussed. Finally, issues pertaining to rates of sulfenic acid formation, reduction, and chemical trapping methods are also covered. Major conclusions Early chemical models of sulfenic acid yielded important insights into the unique reactivity of this species. Subsequent pioneering studies led to the characterization of sulfenic acid formation in proteins. In parallel, the discovery of oxidant-mediated cell signaling pathways and pathological oxidative stress has led to significant interest in methods to detect these modifications. Advanced methods allow for direct chemical trapping of protein sulfenic acids directly in cells and tissues. At the same time, many sulfenic acids are short-lived and the reactivity of current probes must be improved to sample these species, while at the same time, preserving their chemical selectivity. Inhibitors with binding scaffolds can be rationally designed to target sulfenic acid modifications in specific proteins. General significance Ever increasing roles for protein sulfenic acids have been uncovered in physiology and pathology. A more complete understanding of sulfenic acid-mediated regulatory mechanisms will continue to require rigorous and new chemical insights. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and

  14. Acidic deposition and surface water chemistry

    NASA Astrophysics Data System (ADS)

    Church, M. R.

    A pair of back-to-back (morning and afternoon) hydrology sessions, held December 10, 1987, at the AGU Fall Meeting in San Francisco, Calif., covered “Predicting the Effects of Acidic Deposition on Surface Water Chemistry.” The combined sessions included four invited papers, 12 contributed papers, and a panel discussion at its conclusion. The gathering dealt with questions on a variety of aspects of modeling the effects of acidic deposition on surface water chemistry.Contributed papers included discussions on the representation of processes in models as well as limiting assumptions in model application (V. S. Tripathi et al., Oak Ridge National Laboratory, Oak Ridge, Tenn., and E. C. Krug, Illinois State Water Survey, Champaign), along with problems in estimating depositional inputs to catchments and thus inputs to be used in the simulation of catchment response (M. M. Reddy et al., U.S. Geological Survey, Lakewood, Colo.; and E. A. McBean, University of Waterloo, Waterloo, Canada). L. A. Baker et al. (University of Minnesota, Minneapolis) dealt with the problem of modeling seepage lake systems, an exceedingly important portion of the aquatic resources in Florida and parts of the upper U.S. Midwest. J. A. Hau and Y. Eckstein (Kent State University, Kent, Ohio) considered equilibrium modeling of two northern Ohio watersheds that receive very different loads of acidic deposition but are highly similar in other respects.

  15. Understanding atmospheric peroxyformic acid chemistry: observation, modeling and implication

    NASA Astrophysics Data System (ADS)

    Liang, H.; Chen, Z. M.; Huang, D.; Wu, Q. Q.; Huang, L. B.

    2015-01-01

    The existence and importance of peroxyformic acid (PFA) in the atmosphere has been under controversy. We present here, for the first time, the observation data for PFA from four field measurements carried out in China. These data provided powerful evidence that PFA can stay in the atmosphere, typically in dozens of pptv level. The relationship between PFA and other detected peroxides was examined. The results showed that PFA had a strong positive correlation with its homolog, peroxyacetic acid, due to their similar sources and sinks. Through an evaluation of PFA production and removal rates, we proposed that the reactions between peroxyformyl radical (HC(O)O2) and formaldehyde or the hydroperoxyl radical (HO2) were likely to be the major source and degradation into formic acid (FA) was likely to be the major sink for PFA. Based on a box model evaluation, we proposed that the HC(O)O2 and PFA chemistry was a major source for FA under low NOx conditions. Furthermore, it is found that the impact of the HC(O)O2 and PFA chemistry on radical cycling was dependent on the yield of HC(O)O2 radical from HC(O) + O2 reaction. When this yield exceeded 50%, the HC(O)O2 and PFA chemistry should not be neglected for calculating the radical budget. To make clear the exact importance of HC(O)O2 and PFA chemistry in the atmosphere, further kinetic, field and modeling studies are required.

  16. Theme-Based Bidisciplinary Chemistry Laboratory Modules

    NASA Astrophysics Data System (ADS)

    Leber, Phyllis A.; Szczerbicki, Sandra K.

    1996-12-01

    , it will reinforce an understanding of the scientific method by allowing students to propose testable hypotheses based on previous work, and it will generate a large body of quantitative data that can be used to illustrate the fundamentals of data analysis, including statistical measures of uncertainty. We have already developed several "Environmental Chemistry" modules for general chemistry, including monitoring for orthophosphate and nitrate concentrations in water using colorimetric analyses and assaying for gasoline contamination in water and soil samples using GC-MS. Another module dealing with herbicide residues in soil is still being explored. However, we purposefully choose here to emphasize the two modules that are under development for implementation in the organic chemistry laboratory sequence. The first "Plant Assay" project focuses on fatty acid methyl esters (FAMEs) and involves three discrete phases: (i) synthesis and characterization of FAME standards, (ii) isolation of the fatty acids (as FAMEs) from a variety of different plant leaves that will be collected by BIO 110 students on field trips, and (iii) qualitative and quantitative analysis of the plant leaf extract for whole-leaf lipid composition. Acid-catalyzed Fischer esterification of carboxylic acids in methanol is a standard methodology for the preparation of methyl esters. A textbook procedure (1) for the synthesis of ethyl laurate has been employed, with good success, to prepare eight FAMEs in yields of ca. 70%. Conversion of leaf phospholipids to FAMEs proceeds readily via a transesterification reaction. Treatment of the whole leaf in a methanolic HCl solution for an hour at 80 °C (2) is sufficient after extraction in hexane to provide a suitable sample for GC-MS analysis. Preliminary results obtained with an HP GCD system indicate that GC-MS will afford highly reliable quantitative data on FAME lipid composition. Possible extensions of the project include using boron trifluoride in

  17. What Are They Thinking? Automated Analysis of Student Writing about Acid-Base Chemistry in Introductory Biology

    ERIC Educational Resources Information Center

    Haudek, Kevin C.; Prevost, Luanna B.; Moscarella, Rosa A.; Merrill, John; Urban-Lurain, Mark

    2012-01-01

    Students' writing can provide better insight into their thinking than can multiple-choice questions. However, resource constraints often prevent faculty from using writing assessments in large undergraduate science courses. We investigated the use of computer software to analyze student writing and to uncover student ideas about chemistry in an…

  18. Soft Cysteine Signaling Network: The Functional Significance of Cysteine in Protein Function and the Soft Acids/Bases Thiol Chemistry That Facilitates Cysteine Modification.

    PubMed

    Wible, Ryan S; Sutter, Thomas R

    2017-03-20

    The unique biophysical and electronic properties of cysteine make this molecule one of the most biologically critical amino acids in the proteome. The defining sulfur atom in cysteine is much larger than the oxygen and nitrogen atoms more commonly found in the other amino acids. As a result of its size, the valence electrons of sulfur are highly polarizable. Unique protein microenvironments favor the polarization of sulfur, thus increasing the overt reactivity of cysteine. Here, we provide a brief overview of the endogenous generation of reactive oxygen and electrophilic species and specific examples of enzymes and transcription factors in which the oxidation or covalent modification of cysteine in those proteins modulates their function. The perspective concludes with a discussion of cysteine chemistry and biophysics, the hard and soft acids and bases model, and the proposal of the Soft Cysteine Signaling Network: a hypothesis proposing the existence of a complex signaling network governed by layered chemical reactivity and cross-talk in which the chemical modification of reactive cysteine in biological networks triggers the reorganization of intracellular biochemistry to mitigate spikes in endogenous or exogenous oxidative or electrophilic stress.

  19. Mineralogical transformations controlling acid mine drainage chemistry

    SciTech Connect

    Peretyazhko, Tetyana; Zachara, John M.; Boily, Jean F.; Xia, Yuanxian; Gassman, Paul L.; Arey, Bruce W.; Burgos, William D.

    2009-05-30

    The role of Fe(III) minerals in controlling acid mine drainage (AMD) chemistry was studied using samples from two AMD sites [Gum Boot (GB) and Fridays-2 (FR)] located in northern Pennsylvania. Chemical extractions, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to identify and characterize Fe(III) phases. The mineralogical analysis revealed that schwertmannite and goethite were the principal Fe(III) phases in the sediments. Schwertmannite transformation occurred at the GB site where poorly-crystallized goethite rich in surface-bound sulfate was initially formed. In contrast, no schwertmannite transformation occurred at the FR site. The goethite in GB sediments had spherical morphology due to preservation of schwertmannite structure by adsorbed sulfate. Results of chemical extractions showed that poorly-crystallized goethite was subject to further crystallization accompanied by sulfate desorption. Changes in sulfate speciation preceded its desorption, with a conversion of bidentate- to monodentate-bound sulfate surface complexes. Laboratory sediment incubation experiments were conducted to evaluate the effect of mineral transformation on water chemistry. Incubation experiments were carried out with schwertmannite-containing sediments and AMD waters with different pH and chemical composition. The pH decreased to 1.9-2.2 in all suspensions and the concentrations of dissolved Fe and S increased significantly. Regardless of differences in the initial water composition, pH, Fe and S were similar in suspensions of the same sediment. XRD measurements revealed that schwertmannite transformed into goethite in GB and FR sediments during laboratory incubation. The incubation experiment demonstrated that schwertmannite transformation controlled AMD water chemistry during “closed system” laboratory contact.

  20. A catalytic triad is responsible for acid-base chemistry in the Ascaris suum NAD-malic enzyme.

    PubMed

    Karsten, William E; Liu, Dali; Rao, G S Jagannatha; Harris, Ben G; Cook, Paul F

    2005-03-08

    The pH dependence of kinetic parameters of several active site mutants of the Ascaris suum NAD-malic enzyme was investigated to determine the role of amino acid residues likely involved in catalysis on the basis of three-dimensional structures of malic enzyme. Lysine 199 is positioned to act as the general base that accepts a proton from the 2-hydroxyl of malate during the hydride transfer step. The pH dependence of V/K(malate) for the K199R mutant enzyme reveals a pK of 5.3 for an enzymatic group required to be unprotonated for activity and a second pK of 6.3 that leads to a 10-fold loss in activity above the pK of 6.3 to a new constant value up to pH 10. The V profile for K199R is pH independent from pH 5.5 to pH 10 and decreases below a pK of 4.9. Tyrosine 126 is positioned to act as the general acid that donates a proton to the enolpyruvate intermediate to form pyruvate. The pH dependence of V/K(malate) for the Y126F mutant is qualitatively similar to K199R, with a requirement for a group to be unprotonated for activity with a pK of 5.6 and a partial activity loss of about 3-fold above a pK of 6.7 to a new constant value. The Y126F mutant enzyme is about 60000-fold less active than the wild-type enzyme. In contrast to K199R, the V rate profile for Y126F also shows a partial activity loss above pH 6.6. The wild-type pH profiles were reinvestigated in light of the discovery of the partial activity change for the mutant enzymes. The wild-type V/K(malate) pH-rate profile exhibits the requirement for a group to be unprotonated for catalysis with a pK of 5.6 and also shows the partial activity loss above a pK of 6.4. The wild-type V pH-rate profile decreases below a pK of 5.2 and is pH independent from pH 5.5 to pH 10. Aspartate 294 is within hydrogen-bonding distance to K199 in the open and closed forms of malic enzyme. D294A is about 13000-fold less active than the wild-type enzyme, and the pH-rate profile for V/K(malate) indicates the mutant is only active above p

  1. Using Demonstrations Involving Combustion and Acid-Base Chemistry to Show Hydration of Carbon Dioxide, Sulfur Dioxide, and Magnesium Oxide and Their Relevance for Environmental Climate Science

    ERIC Educational Resources Information Center

    Shaw, C. Frank, III; Webb, James W.; Rothenberger, Otis

    2016-01-01

    The nature of acidic and basic (alkaline) oxides can be easily illustrated via a series of three straightforward classroom demonstrations for high school and general chemistry courses. Properties of carbon dioxide, sulfur dioxide, and magnesium oxide are revealed inexpensively and safely. Additionally, the very different kinetics of hydration of…

  2. Case Studies in Systems Chemistry. Final Report. [Includes Complete Case Study, Carboxylic Acid Equilibria

    ERIC Educational Resources Information Center

    Fleck, George

    This publication was produced as a teaching tool for college chemistry. The book is a text for a computer-based unit on the chemistry of acid-base titrations, and is designed for use with FORTRAN or BASIC computer systems, and with a programmable electronic calculator, in a variety of educational settings. The text attempts to present computer…

  3. 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)

  4. Advances in the Biology and Chemistry of Sialic Acids

    PubMed Central

    Chen, Xi; Varki, Ajit

    2010-01-01

    Sialic acids are a subset of nonulosonic acids, which are nine-carbon alpha-keto aldonic acids. Natural existing sialic acid-containing structures are presented in different sialic acid forms, various sialyl linkages, and on diverse underlying glycans. They play important roles in biological, pathological, and immunological processes. Sialobiology has been a challenging and yet attractive research area. Recent advances in chemical and chemoenzymatic synthesis as well as large-scale E. coli cell-based production have provided a large library of sialoside standards and derivatives in amounts sufficient for structure-activity relationship studies. Sialoglycan microarrays provide an efficient platform for quick identification of preferred ligands for sialic acid-binding proteins. Future research on sialic acid will continue to be at the interface of chemistry and biology. Research efforts will not only lead to a better understanding of the biological and pathological importance of sialic acids and their diversity, but could also lead to the development of therapeutics. PMID:20020717

  5. Picosecond mass-selective measurements of phenol-(NH3)n acid-base chemistry in clusters

    NASA Astrophysics Data System (ADS)

    Steadman, Jhobe; Syage, Jack A.

    1990-04-01

    The rate of proton transfer from the acidic S1 state of phenol to the basis solvent (NH3)n was measured as a function of solvent cluster size n. A distinct reaction threshold was observed for solvent size n=5 for 266 nm picosecond excitation. The proton transfer rate was measured to be ka=(60±10 ps)-1 for n=5-7. A competitive recombination rate of k-a =(350±100 ps)-1 occurs for n=5. Additional solvation stabilizes the product side causing the reaction enthalpy and consequently k-a to decrease. No evidence of proton transfer was observed when phenol was seeded in the less basic solvent clusters (CH3OH)n and (H2O)n.

  6. Naturally occurring fatty acids: source, chemistry and uses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural occurring fatty acids are a large and complex class of compounds found in plants and animals. Fatty acids are abundant and of interest because of their renewability, biodegradability, biocompatibility, low cost, and fascinating chemistry. Of the many fatty acids, only 20-25 of them are widel...

  7. Emergence, Learning Difficulties, and Misconceptions in Chemistry Undergraduate Students' Conceptualizations of Acid Strength

    NASA Astrophysics Data System (ADS)

    Tümay, Halil

    2016-03-01

    Philosophical debates about chemistry have clarified that the issue of emergence plays a critical role in the epistemology and ontology of chemistry. In this article, it is argued that the issue of emergence has also significant implications for understanding learning difficulties and finding ways of addressing them in chemistry. Particularly, it is argued that many misconceptions in chemistry may derive from students' failure to consider emergence in a systemic manner by taking into account all relevant factors in conjunction. Based on this argument, undergraduate students' conceptions of acids, and acid strength (an emergent chemical property) were investigated and it was examined whether or not they conceptualized acid strength as an emergent chemical property. The participants were 41 third- and fourth-year undergraduate students. A concept test and semi-structured interviews were used to probe students' conceptualizations and reasoning about acid strength. Findings of the study revealed that the majority of the undergraduate students did not conceptualize acid strength as an emergent property that arises from interactions among multiple factors. They generally focused on a single factor to predict and explain acid strength, and their faulty responses stemmed from their failure to recognize and consider all factors that affect acid strength. Based on these findings and insights from philosophy of chemistry, promoting system thinking and epistemologically sound argumentative discourses among students is suggested for meaningful chemical education.

  8. Chicoric acid: chemistry, distribution, and production

    PubMed Central

    Lee, Jungmin; Scagel, Carolyn F.

    2013-01-01

    Though chicoric acid was first identified in 1958, it was largely ignored until recent popular media coverage cited potential health beneficial properties from consuming food and dietary supplements containing this compound. To date, plants from at least 63 genera and species have been found to contain chicoric acid, and while the compound is used as a processing quality indicator, it may also have useful health benefits. This review of chicoric acid summarizes research findings and highlights gaps in research knowledge for investigators, industry stakeholders, and consumers alike. Additionally, chicoric acid identification, and quantification methods, biosynthesis, processing improvements to increase chicoric acid retention, and potential areas for future research are discussed. PMID:24790967

  9. Chicoric acid: chemistry, distribution, and production

    NASA Astrophysics Data System (ADS)

    Lee, Jungmin; Scagel, Carolyn

    2013-12-01

    Though chicoric acid was first identified in 1958, it was largely ignored until recent popular media coverage cited potential health beneficial properties from consuming food and dietary supplements containing this compound. To date, plants from at least 63 genera and species have been found to contain chicoric acid, and while the compound is used as a processing quality indicator, it may also have useful health benefits. This review of chicoric acid summarizes research findings and highlights gaps in research knowledge for investigators, industry stakeholders, and consumers alike. Additionally, chicoric acid identification and quantification methods, biosynthesis, processing improvements to increase chicoric acid retention, and potential areas for future research are discussed.

  10. Chicoric acid: chemistry, distribution, and production.

    PubMed

    Lee, Jungmin; Scagel, Carolyn F

    2013-01-01

    Though chicoric acid was first identified in 1958, it was largely ignored until recent popular media coverage cited potential health beneficial properties from consuming food and dietary supplements containing this compound. To date, plants from at least 63 genera and species have been found to contain chicoric acid, and while the compound is used as a processing quality indicator, it may also have useful health benefits. This review of chicoric acid summarizes research findings and highlights gaps in research knowledge for investigators, industry stakeholders, and consumers alike. Additionally, chicoric acid identification, and quantification methods, biosynthesis, processing improvements to increase chicoric acid retention, and potential areas for future research are discussed.

  11. Carborane acids. New "strong yet gentle" acids for organic and inorganic chemistry.

    PubMed

    Reed, Christopher A

    2005-04-07

    Icosahedral carborane anions such as CHB11Cl11- are amongst the least coordinating, most chemically inert anions known. They are also amongst the least basic, so their conjugate acids, H(carborane), are superacids (i.e. stronger than 100% H2SO4). Acidity scale measurements indicate that H(CHB11Cl11) is the strongest pure Brønsted acid presently known, surpassing triflic and fluorosulfuric acid. Nevertheless, it is also an extremely gentle acid--because its conjugate base engages in so little chemistry. Carborane acids separate protic acidity from anion nucleophilicity and destructive oxidative capacity in the conjugate base, to a degree not previously achieved. As a result, many long-sought, highly acidic, reactive cations such as protonated benzene (C6H7+), protonated C60(HC60+), tertiary carbocations (R3C+), vinyl cations (R2C=C(+)-R), silylium ions (R3Si+) and discrete hydronium ions (H3O+, H5O2+ etc.) can be readily isolated as carborane salts and characterized at room temperature by X-ray crystallography.

  12. Chemistry and Electrochemistry in Lewis Acid and Superacid Ionic Liquids

    DTIC Science & Technology

    1994-04-30

    LEWIS ACID AND SUPERACID IONIC LIQUIDS PRINCIPAL INVESTIGATOR: Dr. Robert A. Osteryoung Department of Chemistry North Carolina State University...Spectroscopic Study of Anthracene in a Mixed Lewis-Bronsted Acid Ambient Temperature Molten Salt System", Electrochim. Acta, 37, 2615-2628 (1992...investigated. In acidic melts, electrochemical oxidation of anthracene produces a cation radical which exhibits stability similar to that found in "Msuperdry

  13. Heuristic Reasoning in Chemistry: Making decisions about acid strength

    NASA Astrophysics Data System (ADS)

    McClary, LaKeisha; Talanquer, Vicente

    2011-07-01

    The characterization of students' reasoning strategies is of central importance in the development of instructional strategies that foster meaningful learning. In particular, the identification of shortcut reasoning procedures (heuristics) used by students to reduce cognitive load can help us devise strategies to facilitate the development of more analytical ways of thinking. The central goal of this qualitative study was thus to investigate heuristic reasoning as used by organic chemistry college students, focusing our attention on their ability to predict the relative acid strength of chemical compounds represented using explicit composition and structural features (i.e., structural formulas). Our results indicated that many study participants relied heavily on one or more of the following heuristics to make most of their decisions: reduction, representativeness, and lexicographic. Despite having visual access to reach structural information about the substances included in each ranking task, many students relied on isolated composition features to make their decisions. However, the specific characteristics of the tasks seemed to trigger heuristic reasoning in different ways. Although the use of heuristics allowed students to simplify some components of the ranking tasks and generate correct responses, it often led them astray. Very few study participants predicted the correct trends based on scientifically acceptable arguments. Our results suggest the need for instructional interventions that explicitly develop college chemistry students' abilities to monitor their thinking and evaluate the effectiveness of analytical versus heuristic reasoning strategies in different contexts.

  14. Historical perspectives on fatty acid chemistry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fatty acids are basic renewable chemical building blocks that can be used as intermediates for a multitude of products. Today the global value of fatty acids exceeds 18 billion dollars and is expected to increase to nearly 26 billion over the period from 2014-2019. From it auspicious beginnings, the...

  15. Adsorption of perfluoroalkyl acids by carbonaceous adsorbents: Effect of carbon surface chemistry.

    PubMed

    Zhi, Yue; Liu, Jinxia

    2015-07-01

    Adsorption by carbonaceous sorbents is among the most feasible processes to remove perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) from drinking and ground waters. However, carbon surface chemistry, which has long been recognized essential for dictating performance of such sorbents, has never been considered for PFOS and PFOA adsorption. Thus, the role of surface chemistry was systematically investigated using sorbents with a wide range in precursor material, pore structure, and surface chemistry. Sorbent surface chemistry overwhelmed physical properties in controlling the extent of uptake. The adsorption affinity was positively correlated carbon surface basicity, suggesting that high acid neutralizing or anion exchange capacity was critical for substantial uptake of PFOS and PFOA. Carbon polarity or hydrophobicity had insignificant impact on the extent of adsorption. Synthetic polymer-based Ambersorb and activated carbon fibers were more effective than activated carbon made of natural materials in removing PFOS and PFOA from aqueous solutions.

  16. Extraction chemistry of fermentation product carboxylic acid

    SciTech Connect

    Kertes, A.S.; King, C.J.

    1986-02-01

    Within the framework of a program aiming to improve the existing extractive recovery technology of fermentation products, the state of the art is critically reviewed. The acids under consideration are propionic, lactic, pyruvic, succinic, fumaric, maleic, malic, itaconic, tartaric, citric, and isocitric, all obtained by the aerobic fermentation of glucose via the glycolytic pathway and glyoxylate bypass. With no exception, it is the undissociated monomeric acid that is extracted into carbon-bonded and phosphorus-bonded oxygen donor extractants. In the organic phase, the acids are usually dimerized. The extractive transfer process obeys the Nernst law, and the measured partition coefficients range from about 0.003 for aliphatic hydrocarbons to about 2 to 3 for aliphatic alcohols and ketones to about 10 or more for organophosphates. Equally high distribution ratios are measured when long-chain tertiary amines are employed as extractants, forming bulky salts preferentially soluble in the organic phase. 123 references.

  17. Extraction chemistry of fermentation product carboxylic acids

    SciTech Connect

    Kertes, A.S.; King, C.J.

    1986-02-01

    Within the framework of a program aiming to improve the existing extractive recovery technology of fermentation products, the state of the art is critically reviewed. The acids under consideration are propionic, lactic, pyruvic, succinic, fumaric, maleic, malic, itaconic, tartaric, citric, and isocitric, all obtained by the aerobic fermentation of glucose via the glycolytic pathways and glyoxylate bypass. With no exception, it is the undissociated monomeric acid that is extracted into carbon-bonded and phosphorus-bonded oxygen donor extractants. In the organic phase, the acids are usually dimerized. The extractive transfer process obeys the Nernst law, and the measured partition coefficients range from about 0.003 for aliphatic hydrocarbons to about 2 to 3 for aliphatic alcohols and ketones to about 10 or more for organophosphates. Equally high distribution ratios are measured when long-chain tertiary amines are employed as extractants, forming bulky salts preferentially soluble in the organic phase.

  18. Chicoric acid: chemistry, distribution, and production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Though chicoric acid was first identified in 1958, it was largely ignored until recent popular media coverage cited potential health beneficial properties from consuming food and dietary supplements containing this compound. To date, plants from at least 60 genera have been found to contain chicoric...

  19. Structural acid-base chemistry in the metallic state: how μ3-neutralization drives interfaces and helices in Ti21Mn25.

    PubMed

    Stacey, Timothy E; Fredrickson, Daniel C

    2013-08-05

    Intermetallic phases remain a large class of compounds whose vast structural diversity is unaccounted for by chemical theory. A recent resurgence of interest in intermetallics, due to their potential in such applications as catalysis and thermoelectricity, has intensified the need for models connecting their compositions to their structures and stability. In this Article, we illustrate how the μ3-acidity model, an extension of the acid/base concept based on the Method of Moments, offers intuitive explanations for puzzling structural progressions occurring in intermetallics formed between transition metals. Simple CsCl-type structures are frequently observed for phases with near 1:1 ratios of transition metals. However, in two compounds, TiCu and Ti21Mn25, structures are adopted which deviate from this norm. μ3-Acidity analysis shows that the formation of CsCl-type phases in these exceptional systems would yield an imbalance in the acid/base strength pairing, resulting in overneutralization of the weaker partner and thus instability. Intriguing geometrical features emerge in response, which serve to improve the neutralization of the constituent elements. In both TiCu and Ti21Mn25, part of the structure shields weaker acids or bases from their stronger partners by enhancing homoatomic bonding in the sublattice of the weaker acid or base. In TiCu, this protection is accomplished by developing doubled layers of Ti atoms to reduce their heteroatomic contacts. In Ti21Mn25 the structural response is more extreme: Ti-poor TiMn2 domains are formed to guard Mn from the Ti atoms, while the remaining Ti segregates to regions between the TiMn2 domains. The geometrical details of this arrangement fine-tune the acid/base interactions for an even greater level of stability. The most striking of these occurs in the Ti-rich region, where a paucity of Mn neighbors leads to difficulty in achieving strong neutralization. The Ti atoms arrange themselves in helical tubes, maximizing

  20. Acid precipitation chemistry in an urban plume

    SciTech Connect

    Saxena, P.; Arcado, T.D.; Marler, B.L.; Altshuler, S.L. )

    1987-01-01

    In this paper the authors present the results of an ongoing study performed by the Pacific Gas and Electric Company (PGandE) to: investigate the formation, transport and deposition of acidic species in the urban plume from the San Francisco Bay Area (SFBA) and assess the role of two gas-fired electric generation facilities located on the eastern boundary of the SFBA. They present a brief summary of their study area's climate. The network used in this study and our experimental methods are also described. An analysis of wet deposition data collected by our network is presented along with a discussion of the major findings, to date, of our study.

  1. Prebiotic chemistry and nucleic acid replication

    NASA Technical Reports Server (NTRS)

    Orgel, L. E.; Lohrmann, R.

    1974-01-01

    Recent work is reviewed on some reactions that could have occurred on the primitive earth and that could have played a part in the evolution of a self-replicating system. The transition from the primitive atmosphere to the simplest replicating molecules is considered in four stages: (1) the formation of a 'prebiotic soup' of organic precursors, including the purine and pyrimidine bases and the pentose sugars; (2) the condensation of these precursors and inorganic phosphate to form monomeric nucleotides and activated nucleotide derivatives; (3) the polymerization of nucleotide derivatives to oligonucleotides; and (4) the complementary replication of oligonucleotides in a template-directed process that depends on Watson-Crick base pairing.

  2. Experiments on the Multiphase Chemistry of Isocyanic Acid, HNCO.

    NASA Astrophysics Data System (ADS)

    Roberts, J. M.; Liu, Y.

    2015-12-01

    Isocyanic acid, HNCO, has emerged as a potentially important reduced nitrogen compound that is emitted in wildfires, and may have health effect implications. The extent of the health effects depends on the solubility of HNCO in aqueous and non-aqueous solutions and the relative rates of hydrolysis versus carbamylation reactions (for example: HNCO + ROH => H2NC(O)OR). We report here results of studies of HNCO solubility and its reaction in buffered aqueous solutions (pH3), tridecane, and n-octanol at temperatures over the range 5 to 37°C. From these data, the heats of solution and activation energy of hydrolysis are estimated, and a partition coefficient between n-octanol and water at 25°C is greater than 1 for low pH solutions, indicating appreciable portioning to a non-polar phase, but HNCO will be distributed mostly in the aqueous phase at neutral pH. In addition, it was found that the rate of reaction of HNCO with n-octanol was competitive with hydrolysis under physiologically relevant conditions (pH7.4, 37°C), indicating that carbamylation of ROH groups could be significant. Based on these results, research on the carbamylation of other functional groups, and solubility and reaction studies of other isocyanates (e.g. CH3NCO) are warranted. The implications of this multi-phase chemistry for global exposures to wildfire emissions will be discussed.

  3. Context-Based Chemistry: The Salters Approach

    ERIC Educational Resources Information Center

    Bennett, Judith; Lubben, Fred

    2006-01-01

    This paper describes briefly the development and key features of one of the major context-based courses for upper high school students, Salters Advanced Chemistry. It goes on to consider the research evidence on the impact of the course, focusing on teachers' views, and, in particular, on students' affective and cognitive responses. The research…

  4. Model-Based Inquiries in Chemistry

    ERIC Educational Resources Information Center

    Khan, Samia

    2007-01-01

    In this paper, instructional strategies for sustaining model-based inquiry in an undergraduate chemistry class were analyzed through data collected from classroom observations, a student survey, and in-depth problem-solving sessions with the instructor and students. Analysis of teacher-student interactions revealed a cyclical pattern in which…

  5. Investigating Students' Reasoning about Acid-Base Reactions

    ERIC Educational Resources Information Center

    Cooper, Melanie M.; Kouyoumdjian, Hovig; Underwood, Sonia M.

    2016-01-01

    Acid-base chemistry is central to a wide range of reactions. If students are able to understand how and why acid-base reactions occur, it should provide a basis for reasoning about a host of other reactions. Here, we report the development of a method to characterize student reasoning about acid-base reactions based on their description of…

  6. Using Art-Based Chemistry Activities to Improve Students' Conceptual Understanding in Chemistry

    ERIC Educational Resources Information Center

    Danipog, Dennis L.; Ferido, Marlene B.

    2011-01-01

    This study aimed to determine the effects of art-based chemistry activities (ABCA) on high school students' conceptual understanding in chemistry. The study used the pretest-posttest control group design. A total of 64 third-year high school students from two different chemistry classes participated in the study. One class was exposed to art-based…

  7. Microbiology and chemistry of acid lakes in Florida

    SciTech Connect

    James, R.T.

    1989-01-01

    Effects of acid precipitation, low pH, and dissolved organic carbon (DOC), on lake chemistry and microbiology were investigated spatially - in 5 clear and 5 dark lakes, temporally - in 3 clear and 2 dark lakes over a 2 year period, and experimentally - in enclosures to investigate effects of various acid manipulations. Spatial studies found significant positive relationships among DOC, chlorophyll a, pH, and bacterial densities. Using all data, a subsidy stress curve was observed between DOC and bacteria, further indicating toxicity of DOC at high concentrations. Temporal studies found no consistent or significant relationships between pH and bacterial densities, bacterial biomass, chlorophyll a, and protozoans. Clear lake pH was negatively related to rainfall and acid deposition. Acid deposition was also negatively related to glucose assimilation by surface water bacteria, indicating a stress on bacteria. Experimental studies examined effects of pulsed and gradual acid additions on microbial communities of a clear and dark lake. Bacteria biomass and density did not decline in response to any acid addition. Decrease uptake of both glucose and thymidine was observed in the clear-lake pulsed treatment. Chlorophyll a and protozoans declined in the dark lake pulsed treatment but not in others, indicating that pulsed additions of acid were more detrimental to the microbial community than gradual additions to the same pH.

  8. Long-term temporal trends and spatial patterns in the acid-base chemistry of lakes in the Adirondack region of New York in response to decreases in acidic deposition

    NASA Astrophysics Data System (ADS)

    Driscoll, Charles T.; Driscoll, Kimberley M.; Fakhraei, Habibollah; Civerolo, Kevin

    2016-12-01

    We examined the response of lake water chemistry in the Adirondack Mountains of New York State, USA to decreases in acid deposition. Striking declines in the concentrations and fluxes of sulfate and hydrogen ion in wet deposition have been observed since the late 1970s, while significant decreases in nitrate have been evident since the early 2000s. Decreases in estimated dry sulfur and nitrate deposition have also occurred in the Adirondacks, but with no change in dry to wet deposition ratios. These patterns follow long-term decreases in anthropogenic emissions of sulfur dioxide and nitrogen oxides in the U.S. over the same interval. All of the 48 lakes monitored through the Adirondack Long-Term Monitoring program since 1992 have exhibited significant declines in sulfate concentrations, consistent with reductions in atmospheric deposition of sulfur. Nitrate concentrations have also significantly diminished at variable rates in many (33 of 48) lakes. Decreases in concentrations of sulfate plus nitrate (48 of 48) in lakes have driven widespread increases in acid neutralizing capacity (ANC; 42 of 48) and lab pH (33 of 48), and decreases in the toxic fraction, inorganic monomeric Al (45 of 48). Coincident with decreases in acid deposition, concentrations of dissolved organic carbon (DOC) have also increased in some (29 of 48) lakes. While recovery from elevated acid deposition is evident across Adirondack lakes, highly sensitive and impacted mounded seepages lakes and thin till drainage lakes are recovering most rapidly. Future research might focus on how much additional recovery could be achieved given the current deposition relative to future deposition anticipated under the Clean Power Plan, ecosystem effects of increased mobilization of dissolved organic matter, and the influence of changing climate on recovery from acidification.

  9. Wintertime nitric acid chemistry - Implications from three-dimensional model calculations

    NASA Technical Reports Server (NTRS)

    Rood, Richard B.; Kaye, Jack A.; Douglass, Anne R.; Allen, Dale J.; Steenford, Stephen

    1990-01-01

    A three-dimensional simulation of the evolution of HNO3 has been run for the winter of 1979. Winds and temperatures are taken from a stratospheric data assimilation analysis, and the chemistry is based on Limb Infrared Monitor of the Stratosphere (LIMS) observations. The model is compared to LIMS observations to investigate the problem of 'missing' nitric acid chemistry in the winter hemisphere. Both the model and observations support the contention that a nitric acid source is needed outside of the polar vortex and north of the subtropics. Observations suggest that HNO3 is not dynamically controlled in middle latitudes. The model shows that given the time scales of conventional chemistry, dynamical control is expected. Therefore, an error exists in the conventional chemistry or additional processes are needed to bring the model and data into agreement. Since the polar vortex is dynamically isolated from the middle latitudes, and since the highest HNO3 values are observed in October and November, a source associated solely with polar stratospheric clouds cannot explain the deficiencies in the chemistry. The role of heterogeneous processes on background aerosols is reviewed in light of these results.

  10. Acid-base chemistry in the gas phase: The trans-1-naphtholṡNH3 complex in its S0 and S1 electronic states

    NASA Astrophysics Data System (ADS)

    Humphrey, Susan J.; Pratt, David W.

    1996-06-01

    We deduce information about the dynamics of a proton transfer reaction between an acid and a base. Our probe is the fully resolved S1←S0 fluorescence excitation spectrum of the 1:1 complex of 1-naphthol and ammonia in the gas phase. Analysis of this spectrum shows that the complex is planar in both electronic states, with the NH3 forming a nearly linear hydrogen bond to the hydroxy hydrogen atom of 1-naphthol. The O-H...N heavy atom separation is R=2.86 Å and the barrier to rotation of the NH3 group about its C3 axis is V3=39.9 cm-1 in the S0 state. Excitation of the complex to its S1 state increases the acidity of 1-naphthol, decreases the heavy atom separation to R=2.72 Å, and increases the torsional barrier to V3=46.5 cm-1. Modeling these changes using the Lippincott-Schroeder potential for the hydrogen bond shows that the photoinitiated heavy atom motion produces a significant decrease in the barrier to proton transfer in the S1 state.

  11. Acid-base chemistry in the gas phase. The cis- and trans-2-naphtholṡNH3 complexes in their S0 and S1 states

    NASA Astrophysics Data System (ADS)

    Plusquellic, D. F.; Tan, X.-Q.; Pratt, D. W.

    1992-06-01

    A unique view of the nascent acid-base reaction between 2-naphthol and ammonia along the proton transfer coordinate is provided by analyses of the rotationally resolved S1←S0 electronic spectra of their hydrogen bonded complexes cis- and trans-2HNA in the gas phase. Both complexes, in both electronic states, have structures in which ammonia, acting as a base, forms an in-plane hydrogen bond with the hydroxy hydrogen atom of 2-naphthol. The ground state O-HṡṡṡN heavy atom separations are R=2.77 Å in cis-2HNA and R=2.79 Å in trans-2HNA. Electronic excitation of the significantly more acidic S1 state of 2-naphthol produces large decreases in R in both complexes. S1 cis-2HNA has R=2.62 Å and S1 trans-2HNA has R=2.57 Å. Comparing these results to the Lippincott-Schroeder potential for the hydrogen bond shows that there is little change in the vibrationally averaged position of the hydroxy hydrogen atom. But decreasing R produces significant decreases in the barrier to proton transfer, in the distance from reactant to product along the reaction coordinate, and in the energy difference between them. We thus conclude that whether or not such transfer occurs is primarily dependent on the ability of the two heavy atoms to come into close proximity during the early stages of the reaction, a condition that is not satisfied in either cis- or trans-2HNA, in either electronic state. This view is supported by observed changes in the shapes of the potential surfaces along the NH3 torsional coordinate that occur on S1←S0 excitation of the two complexes.

  12. Development and Assessment of a Diagnostic Tool to Identify Organic Chemistry Students' Alternative Conceptions Related to Acid Strength

    ERIC Educational Resources Information Center

    McClary, LaKeisha M.; Bretz, Stacey Lowery

    2012-01-01

    The central goal of this study was to create a new diagnostic tool to identify organic chemistry students' alternative conceptions related to acid strength. Twenty years of research on secondary and college students' conceptions about acids and bases has shown that these important concepts are difficult for students to apply to qualitative problem…

  13. Acid snowpack chemistry in Pennsylvania, 1979-1981

    SciTech Connect

    Dewalle, D.R.; Sharpe, W.E.; Izbicki, J.A.; Wirries, D.L.

    1983-12-01

    Snowpack chemistry was evaluated with repeated surveys at 30 sampling sites across Pennsylvania during 1979-1981. The mean snowpack pH of 4.25 of 280 samples was largely due the H/sup +/ from nitric acid. Snowpack sulfates were high, especially in the southwest sector of the state, where SO/sub 2/ emissions were also high. Rain-on-snow and coastal storm snowpacks produced higher snowpack pH. Localized increases in snowpack pH were found due to additions of dust from limestone and dolomite quarry operations, especially in the central ridge and valley province. Acid loading on the landscape from snow in Pennsylvania is controlled by the total amount of snowfall as well as variations in concentrations of chemical constituents. 16 references, 8 figures, 5 tables.

  14. Acid snowpack chemistry in Pennsylvania, 1979-81

    SciTech Connect

    DeWalle, D.R.; Sharpe, W.E.; Izbicki, J.A.; Wirries, D.L.

    1983-12-01

    Snowpack chemistry was evaluated with repeated surveys at 30 sampling sites across Pennsylvania during 1979-1981. The mean snowpack pH of 4.25 for 280 samples was largely due to H/sup +/ from nitric acid. Snowpack sulfates were high, especially in the southwest sector of the state, where SO/sub 2/ emissions were also high. Rain-on-snow and coastal storm snowpacks produced higher snowpack pH. Localized increases in snowpack pH were found due to additions of dust from limestone and dolomite quarry operations, especially in the central Ridge and Valley Province. Acid loading on the landscape from snow in Pennsylvania is controlled by the total amount of snowfall as well as variations in concentrations of chemical constituents. 16 references, 7 figures, 5 tables.

  15. Acid deposition and atmospheric chemistry at Allegheny Mountain

    SciTech Connect

    Pierson, W.R.; Brachaczek, W.W.; Gorse, R.A. Jr.; Japar, S.M.; Norbeck, J.M.; Keeler, G.J.

    1986-04-01

    In August, 1983 members of the Research Staff of Ford Motor Company carried out a field experiment at two rural sites in southwestern Pennsylvania involving various aspects of the acid deposition phenomenon. This presentation focuses on the wet (rain) deposition during the experiment, as well as the relative importance of wet and dry deposition processes for nitrate and sulfate at the sites. Other aspects of the experiment have been discussed elsewhere: the chemistry of dew and its role in acid deposition (1), the dry deposition of HNO/sub 3/ and SO/sub 2/ to surrogate surfaces (2), and the role of elemental carbon in light absorption and of light absorption in degradation of visibility (3).

  16. 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…

  17. Soil calcium status and the response of stream chemistry to changing acidic deposition rates

    USGS Publications Warehouse

    Lawrence, G.B.; David, M.B.; Lovett, Gary M.; Murdoch, Peter S.; Burns, Douglas A.; Stoddard, J.L.; Baldigo, Barry P.; Porter, J.H.; Thompson, A.W.

    1999-01-01

    Despite a decreasing trend in acidic deposition rates over the past two to three decades, acidified surface waters in the northeastern United States have shown minimal changes. Depletion of soil Ca pools has been suggested as a cause, although changes in soil Ca pools have not been directly related to long-term records of stream chemistry. To investigate this problem, a comprehensive watershed study was conducted in the Neversink River Basin, in the Catskill Mountains of New York, during 1991-1996. Spatial variations of atmospheric deposition, soil chemistry, and stream chemistry were evaluated over an elevation range of 817-1234 m to determine whether these factors exhibited elevational patterns. An increase in atmospheric deposition of SO4 with increasing elevation corresponded with upslope decreases of exchangeable soil base concentrations and acid-neutralizing capacity of stream water. Exchangeable base concentrations in homogeneous soil incubated within the soil profile for one year also decreased with increasing elevation. An elevational gradient in precipitation was not observed, and effects of a temperature gradient on soil properties were not detected. Laboratory leaching experiments with soils from this watershed showed that (1) concentrations of Ca in leachate increased as the concentrations of acid anions in added solution increased, and (2) the slope of this relationship was positively correlated with base saturation. Field and laboratory soil analyses are consistent with the interpretation that decreasing trends in acid-neutralizing capacity in stream water in the Neversink Basin, dating back to 1984, are the result of decreases in soil base saturation caused by acidic deposition.

  18. Sulfuric Acid Monohydrate: Formation and Heterogeneous Chemistry in the Stratosphere

    NASA Technical Reports Server (NTRS)

    Zhang, Renyi; Leu, Ming-Taun; Keyser, Leon F.

    1995-01-01

    We have investigated some thermodynamic properties (i.e., freezing/melting points) and heterogeneous chemistry of sulfuric acid monohydrate (SAM, H2SO4.H2O), using a fast flow reactor coupled to a quadrupole mass spectrometer. The freezing point observations of thin liquid sulfuric acid films show that for acid contents between 75 and 85 wt % the monohydrate crystallizes readily at temperatures between 220 and 240 K on a glass substrate. Once formed, SAM can be thermodynamically stable in the H2O partial pressure range of (1-4) x 10(exp -4) torr and in the temperature range of 220-240 K. For a constant H2O partial pressure, lowering the temperature causes SAM to melt when the temperature and water partial pressure conditions are out of its stability regime. The reaction probability measurements indicate that the hydrolysis of N2O5 is significantly suppressed owing to the formation of crystalline SAM: The reaction probability on water-rich SAM (with higher relative humidity, or RH) is of the order of 10(exp -3) at 210 K and decreases by more than an order of magnitude for the acid-rich form (with lower RH). The hydrolysis rate of ClONO2 on water-rich SAM is even smaller, of the order of 10(exp -4) at 195 K. These reported values on crystalline SAM are much smaller than those on liquid solutions. No enhancement of these reactions is observed in the presence of HCl vapor at the stratospheric concentrations. In addition, Brunauer, Emmett, and Teller analysis of gas adsorption isotherms and photomicrography have been performed to characterize the surface roughness and porosities of the SAM substrate. The results suggest the possible formation of SAM in some regions of the middle- or low-latitude stratosphere and, consequently, much slower heterogeneous reactions on the frozen aerosols.

  19. Acid rain and atmospheric chemistry at Allegheny Mountain

    SciTech Connect

    Pierson, W.R.; Brachaczek, W.W.; Gorse, R.A. Jr.; Japar, S.M.; Norbeck, J.M.; Keeler, G.J.

    1987-07-01

    Rain chemistry was measured in August 1983 on Allegheny Mountain and Larel Hill in southwester Pennsylvania. The average composition approximated an H/sub 2/SO/sub 5//HNO/sub 3/ mixture with a volume-weighted average pH of 3.5 and an SO/sub 4//sup 2 -//NO/sub 3//sup -/ mole ratio of 1.8. There was very little undissociated (weak) acidity and very little S(IV). The acidic rains were associated with air masses traversing SO/sub 2/ source regions west of the sites; stagnation and intervening precipitation were important influences. The geographic scale for a halving of rain SO/sub 4//sup 2 -/ concentration downwind of SO/sub 2/ sources was approx.440 km. Scavenging ratios were inferred for SO/sub 2/, aerosol SO/sub 4//sup 2 -/, and HNO/sub 3/. On average about half of the rain SO/sub 4//sup 2 -/ resulted from scavenging of SO/sub 2/, the rest from scavenging of SO/sub 4//sup 2 -/. The rain H/sup +/ was attributed about 25% to HNO/sub 3/, 55% to scavenging of SO/sub 2/, and 20% to scavenging of aerosol acid SO/sub 4//sup 2 -/. Cumulative deposition totals in rain were compared with deposition in fog and with dry deposition in the same experiment. A crude acid-deposition budget was calculated as follows: 47%, H/sub 2/SO/sub 4/ in rain; 23%, SO/sub 2/ dry deposition without dew; 16%, HNO/sub 3/ in rain; 11%, HNO/sub 3/ dry deposition without dew; 2%, HNO/sub 3/ and H/sub 2/SO/sub 4/ in fog and dew; 0.5%, aerosol dry deposition without dew. 86 references, 4 figures, 8 tables.

  20. Whole body acid-base modeling revisited.

    PubMed

    Ring, Troels; Nielsen, Søren

    2017-04-01

    The textbook account of whole body acid-base balance in terms of endogenous acid production, renal net acid excretion, and gastrointestinal alkali absorption, which is the only comprehensive model around, has never been applied in clinical practice or been formally validated. To improve understanding of acid-base modeling, we managed to write up this conventional model as an expression solely on urine chemistry. Renal net acid excretion and endogenous acid production were already formulated in terms of urine chemistry, and we could from the literature also see gastrointestinal alkali absorption in terms of urine excretions. With a few assumptions it was possible to see that this expression of net acid balance was arithmetically identical to minus urine charge, whereby under the development of acidosis, urine was predicted to acquire a net negative charge. The literature already mentions unexplained negative urine charges so we scrutinized a series of seminal papers and confirmed empirically the theoretical prediction that observed urine charge did acquire negative charge as acidosis developed. Hence, we can conclude that the conventional model is problematic since it predicts what is physiologically impossible. Therefore, we need a new model for whole body acid-base balance, which does not have impossible implications. Furthermore, new experimental studies are needed to account for charge imbalance in urine under development of acidosis.

  1. Modeling aluminum-silicon chemistries and application to Australian acidic playa lakes as analogues for Mars

    USGS Publications Warehouse

    Marion, G.M.; Crowley, J.K.; Thomson, B.J.; Kargel, J.S.; Bridges, N.T.; Hook, S.J.; Baldridge, A.; Brown, A.J.; Ribeiro da Luz, B.; de Souza, Filho C.R.

    2009-01-01

    Recent Mars missions have stimulated considerable thinking about the surficial geochemical evolution of Mars. Among the major relevant findings are the presence in Meridiani Planum sediments of the mineral jarosite (a ferric sulfate salt) and related minerals that require formation from an acid-salt brine and oxidizing environment. Similar mineralogies have been observed in acidic saline lake sediments in Western Australia (WA), and these lakes have been proposed as analogues for acidic sedimentary environments on Mars. The prior version of the equilibrium chemical thermodynamic FREZCHEM model lacked Al and Si chemistries that are needed to appropriately model acidic aqueous geochemistries on Earth and Mars. The objectives of this work were to (1) add Al and Si chemistries to the FREZCHEM model, (2) extend these chemistries to low temperatures (<0 ??C), if possible, and (3) use the reformulated model to investigate parallels in the mineral precipitation behavior of acidic Australian lakes and hypothetical Martian brines. FREZCHEM is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the Pitzer approach for the temperature range from <-70 to 25 ??C and the pressure range from 1 to 1000 bars. Aluminum chloride and sulfate mineral parameterizations were based on experimental data. Aluminum hydroxide and silicon mineral parameterizations were based on Gibbs free energy and enthalpy data. New aluminum and silicon parameterizations added 12 new aluminum/silicon minerals to this Na-K-Mg-Ca-Fe(II)-Fe(III)-Al-H-Cl-Br-SO4-NO3-OH-HCO3-CO3-CO2-O2-CH4-Si-H2O system that now contain 95 solid phases. There were similarities, differences, and uncertainties between Australian acidic, saline playa lakes and waters that likely led to the Burns formation salt accumulations on Mars. Both systems are similar in that they are dominated by (1) acidic, saline ground waters and sediments, (2) Ca and/or Mg sulfates, and (3) iron

  2. Modeling aluminum-silicon chemistries and application to Australian acidic playa lakes as analogues for Mars

    NASA Astrophysics Data System (ADS)

    Marion, G. M.; Crowley, J. K.; Thomson, B. J.; Kargel, J. S.; Bridges, N. T.; Hook, S. J.; Baldridge, A.; Brown, A. J.; Ribeiro da Luz, B.; de Souza Filho, C. R.

    2009-06-01

    Recent Mars missions have stimulated considerable thinking about the surficial geochemical evolution of Mars. Among the major relevant findings are the presence in Meridiani Planum sediments of the mineral jarosite (a ferric sulfate salt) and related minerals that require formation from an acid-salt brine and oxidizing environment. Similar mineralogies have been observed in acidic saline lake sediments in Western Australia (WA), and these lakes have been proposed as analogues for acidic sedimentary environments on Mars. The prior version of the equilibrium chemical thermodynamic FREZCHEM model lacked Al and Si chemistries that are needed to appropriately model acidic aqueous geochemistries on Earth and Mars. The objectives of this work were to (1) add Al and Si chemistries to the FREZCHEM model, (2) extend these chemistries to low temperatures (<0 °C), if possible, and (3) use the reformulated model to investigate parallels in the mineral precipitation behavior of acidic Australian lakes and hypothetical Martian brines. FREZCHEM is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions using the Pitzer approach for the temperature range from <-70 to 25 °C and the pressure range from 1 to 1000 bars. Aluminum chloride and sulfate mineral parameterizations were based on experimental data. Aluminum hydroxide and silicon mineral parameterizations were based on Gibbs free energy and enthalpy data. New aluminum and silicon parameterizations added 12 new aluminum/silicon minerals to this Na-K-Mg-Ca-Fe(II)-Fe(III)-Al-H-Cl-Br-SO 4-NO 3-OH-HCO 3-CO 3-CO 2-O 2-CH 4-Si-H 2O system that now contain 95 solid phases. There were similarities, differences, and uncertainties between Australian acidic, saline playa lakes and waters that likely led to the Burns formation salt accumulations on Mars. Both systems are similar in that they are dominated by (1) acidic, saline ground waters and sediments, (2) Ca and/or Mg sulfates, and (3) iron

  3. Plants and Chemistry: A Teaching Course Based on the Chemistry of Substances of Plant Origin

    NASA Astrophysics Data System (ADS)

    Andreoli, Katia; Calascibetta, Franco; Campanella, Luigi; Favero, Gabriele; Occhionero, Francesca

    2002-08-01

    Over the past few years, we developed an idea about the teaching of chemistry by determining the links between theory and the real world. The principles, concepts, and experimental procedures of chemistry were illustrated through an original approach based on useful substances obtained from plants. The starting point was substances that have always been obtained from trees and vegetables. The approach was implemented during many refresher courses for secondary school teachers of chemistry. The courses were divided into sections, each called "Plants and ...", dedicated to colors, odors, tastes, medicines and drugs, fibers, soaps, and alcoholic beverages. Each section consisted of a theoretical lesson followed by a laboratory session.

  4. Using Diagnostic Assessment to Help Teachers Understand the Chemistry of the Lead-Acid Battery

    ERIC Educational Resources Information Center

    Cheung, Derek

    2011-01-01

    Nineteen pre-service and in-service teachers taking a chemistry teaching methods course at a university in Hong Kong were asked to take a diagnostic assessment. It consisted of seven multiple-choice questions about the chemistry of the lead-acid battery. Analysis of the teachers' responses to the questions indicated that they had difficulty in…

  5. [Recent progress on analytical chemistry and biochemistry of D-amino acids].

    PubMed

    Imai, K; Kato, M; Huang, Y; Ichihara, H; Fukushima, T; Santa, T; Homma, H

    1997-11-01

    Recent findings that D-amino acids, especially D-aspartic acid and D-serine, exist in vivo in the mammalian tissues (brain and peripheries), prompted us now to investigate their biological and pathological roles in mammals. In this review, the overview of the progress of analytical chemistry and biochemistry of D-amino acids is described.

  6. Computational Modeling of the Optical Rotation of Amino Acids: An "in Silico" Experiment for Physical Chemistry

    ERIC Educational Resources Information Center

    Simpson, Scott; Autschbach, Jochen; Zurek, Eva

    2013-01-01

    A computational experiment that investigates the optical activity of the amino acid valine has been developed for an upper-level undergraduate physical chemistry laboratory course. Hybrid density functional theory calculations were carried out for valine to confirm the rule that adding a strong acid to a solution of an amino acid in the l…

  7. Implementation of Problem-Based Learning in Environmental Chemistry

    ERIC Educational Resources Information Center

    Jansson, Stina; So¨derstro¨m, Hanna; Andersson, Patrik L.; Nording, Malin L.

    2015-01-01

    Environmental Chemistry covers a range of topics within the discipline of chemistry, from toxicology to legislation, which warrants interdisciplinary study. Consequently, problem-based learning (PBL), a style of student-centered learning which facilitates the integration of multiple subjects, was investigated to determine if it would be a more…

  8. An Evidence-Based Approach to Introductory Chemistry

    ERIC Educational Resources Information Center

    Johnson, Philip

    2014-01-01

    Drawing on research into students' understanding, this article argues that the customary approach to introductory chemistry has created difficulties for students. Instead of being based on the notion of "solids, liquids and gases", introductory chemistry should be structured to develop the concept of a substance. The concept of a…

  9. Radiation chemistry of salicylic and methyl substituted salicylic acids: Models for the radiation chemistry of pharmaceutical compounds

    NASA Astrophysics Data System (ADS)

    Ayatollahi, Shakiba; Kalnina, Daina; Song, Weihua; Turks, Maris; Cooper, William J.

    2013-11-01

    Salicylic acid and its derivatives are components of many medications and moieties found in numerous pharmaceutical compounds. They have been used as models for various pharmaceutical compounds in pharmacological studies, for the treatment of pharmaceuticals and personal care products (PPCPs), and, reactions with natural organic matter (NOM). In this study, the radiation chemistry of benzoic acid, salicylic acid and four methyl substituted salicylic acids (MSA) is reported. The absolute bimolecular reaction rate constants for hydroxyl radical reaction with benzoic and salicylic acids as well as 3-methyl-, 4-methyl-, 5-methyl-, and 6-methyl-salicylic acid were determined (5.86±0.54)×109, (1.07±0.07)×1010, (7.48±0.17)×109, (7.31±0.29)×109, (5.47±0.25)×109, (6.94±0.10)×109 (M-1 s-1), respectively. The hydrated electron reaction rate constants were measured (3.02±0.10)×109, (8.98±0.27)×109, (5.39±0.21)×109, (4.33±0.17)×109, (4.72±0.15)×109, (1.42±0.02)×109 (M-1 s-1), respectively. The transient absorption spectra for the six model compounds were examined and their role as model compounds for the radiation chemistry of pharmaceuticals investigated.

  10. Amino Acid Chemistry as a Link Between Small Solar System Bodies and Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Ehrenfreund, Pascale; Botta, Oliver; Cooper, George; Bada, Jeffrey L.

    2000-01-01

    and comets replenish the NEO population, therefore extinct comets may contribute up to half of all NEO's. A comparison of an amino acid analysis of a returned NEO sample to CI and CM carbonaceous chondrites would help establish a link between small solar system bodies and meteorites. Based on our amino acid measurements of CI and CM chondrites, amino acid chemistry can be included as an additional set of criteria to constrain the nature of meteorite parent bodies.

  11. [Stewart's acid-base approach].

    PubMed

    Funk, Georg-Christian

    2007-01-01

    In addition to paCO(2), Stewart's acid base model takes into account the influence of albumin, inorganic phosphate, electrolytes and lactate on acid-base equilibrium. It allows a comprehensive and quantitative analysis of acid-base disorders. Particularly simultaneous and mixed metabolic acid-base disorders, which are common in critically ill patients, can be assessed. Stewart's approach is therefore a valuable tool in addition to the customary acid-base approach based on bicarbonate or base excess. However, some chemical aspects of Stewart's approach remain controversial.

  12. GC-MS Analysis of [gamma]-Hydroxybutyric Acid Analogs: A Forensic Chemistry Experiment

    ERIC Educational Resources Information Center

    Henck, Colin; Nally, Luke

    2007-01-01

    An upper-division forensic chemistry experiment is described. It involves using glycolic acid and sodium glycolate as analogs of [gamma]-hydroxybutyric acid and its sodium salt. The experiment shows the use of silylation in GC-MS analysis and gives students the opportunity to work with a commonly used silylating reagent,…

  13. The Correlation of Binary Acid Strengths with Molecular Properties in First-Year Chemistry

    ERIC Educational Resources Information Center

    Fridgen, Travis D.

    2008-01-01

    This article deals with the rather complicated if not incorrect way that the strengths of binary acids are rationalized to students in many classrooms owing to the way it is presented in first-year chemistry textbooks. The common explanations, which use the homolytic bond dissociation energy as a rationalization of the trend in acid strengths when…

  14. Ceria-based solid catalysts for organic chemistry.

    PubMed

    Vivier, Laurence; Duprez, Daniel

    2010-06-21

    Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases. However, ceria-based catalysts have also been developed for different applications in organic chemistry. The redox and acid-base properties of ceria, either alone or in the presence of transition metals, are important parameters that allow to activate complex organic molecules and to selectively orient their transformation. Pure ceria is used in several organic reactions, such as the dehydration of alcohols, the alkylation of aromatic compounds, ketone formation, and aldolization, and in redox reactions. Ceria-supported metal catalysts allow the hydrogenation of many unsaturated compounds. They can also be used for coupling or ring-opening reactions. Cerium atoms can be added as dopants to catalytic system or impregnated onto zeolites and mesoporous catalyst materials to improve their performances. This Review demonstrates that the exceptional surface (and sometimes bulk) properties of ceria make cerium-based catalysts very effective for a broad range of organic reactions.

  15. Surface chemistry of Cu(100) in acidic sulfate solutions

    NASA Astrophysics Data System (ADS)

    Ehlers, Charles B.; Stickney, John L.

    1990-12-01

    The surface chemistry of Cu(100), in H 2SO 4 and acidic K 2SO 4 solutions, has been studied by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and thermal desorption spectroscopy (TDS). Experiments were conducted in an electrochemical cell coupled directly to a UHV surface analysis chamber. Structures formed on the Cu(100) surface emersed (removed) from sulfate solutions were the principal focus of this study. Structures and coverages were primarily dependent on sulfate concentration and the presence of coadsorbates such as Cl and K +. Emersion of Cu(100) from 1 mM H 2SO 4 resulted in a Cu(100)(2 × 2)-SO 2-4 adlattice with a {1}/{4} coverage of sulfate. A {1}/{5} coverage Cu(100)( 5 × 5) R26.6°- SO2-4 structure formed upon emersion mM H 2SO 4 containing trace Cl - contaminants, and a {1}/{3} coverage Cu(100)(2 × 100)- SO2-4 structure formed following e from 10 mM H 2SO 4. Emersion of Cu(100) from 1 mM K 2SO 4 (pH = 3.6) resulted in a Cu(100)(4 × 2 5)- SO2-4, K + surface structure, with K + and SO 2-4 coadsorbed in a 1:1 stoichiometry, each at {1}/{4} coverage. No significant potential-dependent variatio in surface structure or coverage was observed when the electrode was emersed from H 2SO 4 at potentials in the double-layer charging region. For emersion from 1 mM K 2SO 4 (pH = 3.6), a reduction in K + coverage along with a change in the surface structure to a (2 × 2) occurred at positive potentials. Comparisons were made of sulfate adsorption on the low-index planes of Cu using a Cu single crystal polished on three different faces to the (111), (110) and (100) planes. This electrode was emersed from 1 mM K 2SO 4 (pH = 3.6) at several potentials. A c(8 × 2) and a diffuse (1 × 1) LEED pattern were observed on Cu(110) and Cu(111), respectively. The K + and SO 2-4 coverages differed appreciably between the three surfaces. Significant differences were observed in the thermal desorption spectra of Cu(100) emersed from H 2SO 4 and K 2SO

  16. Real World of Industrial Chemistry: An Acid Can Be Basic.

    ERIC Educational Resources Information Center

    Fernelius, W. Conard, Ed.; And Others

    1979-01-01

    The uses of sulfuric acid in our technological society are given. The discussion includes sulfuric acid in the petroleum industry, construction industry, textile industry and in steel production. (SA)

  17. Allied Health Chemistry Laboratory: Amino Acids, Insulin, Proteins, and Skin

    ERIC Educational Resources Information Center

    Dever, David F.

    1975-01-01

    Presents a laboratory experiment specifically designed for allied health students. The students construct molecular models of amino acids, extract amino acids from their skin with hot water, and chromatographically analyze the skin extract and hydrolyzed insulin. (MLH)

  18. Teaching Relative Acidity in the Undergraduate Organic Chemistry Course.

    ERIC Educational Resources Information Center

    Traynham, James G.

    1988-01-01

    Described is a teaching method for connecting relative acidity among various species by the use of familiar references. Considered are teaching the acidity of alpha-hydrogens of ketones, alkylation of amides and imides, and others. (CW)

  19. In Situ Click Chemistry for the Identification of a Potent D-Amino Acid Oxidase Inhibitor.

    PubMed

    Toguchi, Shohei; Hirose, Tomoyasu; Yorita, Kazuko; Fukui, Kiyoshi; Sharpless, K Barry; Ōmura, Satoshi; Sunazuka, Toshiaki

    2016-07-01

    In situ click chemistry is a target-guided synthesis approach for discovering novel lead compounds by assembling organic azides and alkynes into triazoles inside the affinity site of target biogenic molecules such as proteins. We report in situ click chemistry screening with human D-amino acid oxidase (hDAO), which led to the identification of a more potent hDAO inhibitor. The hDAO inhibitors have chemotherapeutic potential as antipsychotic agents. The new inhibitor displayed competitive inhibition of hDAO and showed significantly increased inhibitory activity against hDAO compared with that of an anchor molecule of in situ click chemistry.

  20. A Thematic Review of Studies into the Effectiveness of Context-Based Chemistry Curricula

    ERIC Educational Resources Information Center

    Ultay, Neslihan; Calik, Muammer

    2012-01-01

    Context-based chemistry education aims at making connections between real life and the scientific content of chemistry courses. The purpose of this study was to evaluate context-based chemistry studies. In looking for the context-based chemistry studies, the authors entered the keywords "context-based", "contextual learning" and "chemistry…

  1. 100% thiol-functionalized ethylene PMOs prepared by "thiol acid-ene" chemistry.

    PubMed

    Esquivel, Dolores; van den Berg, Otto; Romero-Salguero, Francisco J; Du Prez, Filip; Van der Voort, Pascal

    2013-03-21

    A novel thiol functionalized bis-silane PMO precursor was synthesized by highly efficient thiol acid-ene chemistry between the double bonds of 1,2-(E)-bis(triethoxysilyl)ethene and thioacetic acid. After aminolysis the self-assembly process of the formed SH-precursor with Pluronic P123 under acidic conditions yields the first 100% thiol-PMO material with good structural ordering.

  2. [Research on compatibility chemistry of acid-alkaline pair medicines in formulas of traditional Chinese medicine].

    PubMed

    Pei, Miaorong; Duan, Xiujun; Pei, Xiangping; Xuan, Chunsheng; Wang, Xiaoying; Zhao, Lina; Zhang, Shurong; Liu, Bingchen; Wang, Shimin

    2009-08-01

    Compatibility chemistry of acid-alkaline pair medicines in formulas of traditional Chinese medicine (TCM) is an important research field which should merit to pay attention. The ideas and methods in prescription compatibility research on formulas containing alkaline-acid pair medicines were summarized from the aspect of chemical groups of alkaline and acid ingredients; the research results were introduced and analyzed; the research meaning was elaborated; and the expectation of the field was viewed.

  3. Water chemistry-based classification of streams and implications for restoring mined Appalachian watersheds

    SciTech Connect

    Merovich, G.T.; Stiles, J.M.; Petty, J.T.; Ziemkiewicz, P.F.; Fulton, J.B.

    2007-07-15

    We analyzed seasonal water samples from the Cheat and Tygart Valley river basins, West Virginia, USA, in an attempt to classify streams based on water chemistry in this coal-mining region. We also examined temporal variability among water samples. Principal component analysis identified two important dimensions of variation in water chemistry. This variation was determined largely by mining-related factors (elevated metals, sulfates, and conductivity) and an alkalinity-hardness gradient. Cluster analysis grouped water samples into six types that we described as reference, soft, hard, transitional, moderate acid mine drainage, and severe acid mine drainage. These types were statistically distinguishable in multidimensional space. Classification tree analysis confirmed that chemical constituents related to acid mine drainage and acid rain distinguished these six groups. Hard, soft, and severe acid mine drainage type streams were temporally constant compared to streams identified as reference, transitional, and moderate acid mine drainage type, which had a greater tendency to shift to a different water type between seasons. Our research is the first to establish a statistically supported stream classification system in mined watersheds. The results suggest that human-related stressors superimposed on geology are responsible for producing distinct water quality types in this region as opposed to more continuous variation in chemistry that would be expected in an unimpacted setting. These findings provide a basis for simplifying stream monitoring efforts, developing generalized remediation strategies, and identifying specific remediation priorities in mined Appalachian watersheds.

  4. Water chemistry-based classification of streams and implications for restoring mined Appalachian watersheds.

    PubMed

    Merovich, George T; Stiles, James M; Petty, J Todd; Ziemkiewicz, Paul F; Fulton, Jennifer B

    2007-07-01

    We analyzed seasonal water samples from the Cheat and Tygart Valley river basins, West Virginia, USA, in an attempt to classify streams based on water chemistry in this coal-mining region. We also examined temporal variability among water samples. Principal component analysis identified two important dimensions of variation in water chemistry. This variation was determined largely by mining-related factors (elevated metals, sulfates, and conductivity) and an alkalinity-hardness gradient. Cluster analysis grouped water samples into six types that we described as reference, soft, hard, transitional, moderate acid mine drainage, and severe acid mine drainage. These types were statistically distinguishable in multidimensional space. Classification tree analysis confirmed that chemical constituents related to acid mine drainage and acid rain distinguished these six groups. Hard, soft, and severe acid mine drainage type streams were temporally constant compared to streams identified as reference, transitional, and moderate acid mine drainage type, which had a greater tendency to shift to a different water type between seasons. Our research is the first to establish a statistically supported stream classification system in mined watersheds. The results suggest that human-related stressors superimposed on geology are responsible for producing distinct water quality types in this region as opposed to more continuous variation in chemistry that would be expected in an unimpacted setting. These findings provide a basis for simplifying stream monitoring efforts, developing generalized remediation strategies, and identifying specific remediation priorities in mined Appalachian watersheds.

  5. 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…

  6. Evolution in Medicinal Chemistry of Ursolic Acid Derivatives as Anticancer Agents

    PubMed Central

    Chen, Haijun; Gao, Yu; Wang, Ailan; Zhou, Xiaobin; Zheng, Yunquan; Zhou, Jia

    2015-01-01

    Currently, there is a renewed interest in common dietaries and plant-based traditional medicines for the prevention and treatment of cancer. In the search for potential anticancer agents from natural sources, ursolic acid (UA), a pentacyclic triterpenoid widely found in various medicinal herbs and fruits, exhibits powerful biological effects including its attractive anticancer activity against various types of cancer cells. However, the limited solubility, rapid metabolism and poor bioavailability of UA restricted its further clinical applications. In the past decade, with substantial progress toward the development of new chemical entities for the treatment of cancer, numerous UA derivatives have been designed and prepared to overcome its disadvantages. Despite extensive effort, discovery of effective UA derivatives has so far met with only limited success. This review summarizes the current status of the structural diversity and evolution in medicinal chemistry of UA analogues and provides a detailed discussion of future direction for further research in the chemical modifications of UA. PMID:25617694

  7. Evolution in medicinal chemistry of ursolic acid derivatives as anticancer agents.

    PubMed

    Chen, Haijun; Gao, Yu; Wang, Ailan; Zhou, Xiaobin; Zheng, Yunquan; Zhou, Jia

    2015-03-06

    Currently, there is a renewed interest in common dietaries and plant-based traditional medicines for the prevention and treatment of cancer. In the search for potential anticancer agents from natural sources, ursolic acid (UA), a pentacyclic triterpenoid widely found in various medicinal herbs and fruits, exhibits powerful biological effects including its attractive anticancer activity against various types of cancer cells. However, the limited solubility, rapid metabolism and poor bioavailability of UA restricted its further clinical applications. In the past decade, with substantial progress toward the development of new chemical entities for the treatment of cancer, numerous UA derivatives have been designed and prepared to overcome its disadvantages. Despite extensive effort, discovery of effective UA derivatives has so far met with only limited success. This review summarizes the current status of the structural diversity and evolution in medicinal chemistry of UA analogues and provides a detailed discussion of future direction for further research in the chemical modifications of UA.

  8. Gamma irradiation of isocitric and citric acid in aqueous solution: Relevance in prebiotic chemistry

    NASA Astrophysics Data System (ADS)

    Negrón-Mendoza, A.; Ramos-Bernal, S.

    2015-07-01

    The radiation chemistry of hydroxy acids like citric and isocitric acids is rather scarce, even though they are crucial compounds in biological systems and for food irradiation. The aim of this work is to study the radiolytic behavior of these acids focused on the interconversion induced by radiation of citric and isocitric acid into other members of the Krebs cycle. The results showed that among the products formed were succinic, malonic, malic and other acids related to metabolic pathways, and these results are correlated with its possible role in chemical evolution processes.

  9. Gamma irradiation of isocitric and citric acid in aqueous solution: Relevance in prebiotic chemistry

    SciTech Connect

    Negrón-Mendoza, A. Ramos-Bernal, S.

    2015-07-23

    The radiation chemistry of hydroxy acids like citric and isocitric acids is rather scarce, even though they are crucial compounds in biological systems and for food irradiation. The aim of this work is to study the radiolytic behavior of these acids focused on the interconversion induced by radiation of citric and isocitric acid into other members of the Krebs cycle. The results showed that among the products formed were succinic, malonic, malic and other acids related to metabolic pathways, and these results are correlated with its possible role in chemical evolution processes.

  10. Weak vs Strong Acids and Bases: The Football Analogy

    NASA Astrophysics Data System (ADS)

    Silverstein, Todd P.

    2000-07-01

    An important topic in any introductory chemistry course is that of acids and bases. Students generally have no trouble learning the Brønsted-Lowry definition of an acid as a proton donor and a base as a proton acceptor. Problems often arise, however, when chemistry teachers attempt to explain the difference between weak and strong acids, and between weak and strong bases. For acids in aqueous solution, discussing complete in contrast to partial ionization works well for those with a strong grasp of the equilibrium concept, but for many students it does not seem to do the trick. Partial ionization may not evoke much in the mind of a "visual learner". Accordingly, I have developed a football analogy for acids and bases in which acids are compared to quarterbacks, whose job is to get rid of the ball (H+). A strong acid, like an excellent quarterback, delivers the ball effectively; a weak acid, like a poor quarterback, is often left holding the ball. Furthermore, bases may be likened to wide receivers, whose job is to catch and hold onto the ball (H+). A strong base, like an excellent wide receiver, holds onto the ball; a weak base, like a poor receiver, often drops the ball. The concept of throwing and catching a ball is easy to visualize and the analogy to acids and bases can help even students unfamiliar with the mores of the gridiron to comprehend the mores of aqueous protons.

  11. Simple thiol-ene click chemistry modification of SBA-15 silica pores with carboxylic acids.

    PubMed

    Bordoni, Andrea V; Lombardo, M Verónica; Regazzoni, Alberto E; Soler-Illia, Galo J A A; Wolosiuk, Alejandro

    2015-07-15

    A straightforward approach for anchoring tailored carboxylic groups in mesoporous SiO2 colloidal materials is presented. The thiol-ene photochemical reaction between vinyltrimethoxysilane precursors and various thiocarboxylic acids which has, click chemistry features (i.e. high conversion yields, insensitivity to oxygen, mild reaction conditions), results in carboxylated silane precursors that can be readily used as surface modifiers. The carboxylic groups of acetic, undecanoic and succinic acid were immobilized on the silica mesopore walls of SBA-15 powders employing the synthesized silane precursors. Post-grafting has been confirmed through infrared spectrometry (FTIR), energy dispersive X-ray spectroscopy (EDS), elemental analysis (EA) and zeta potential measurements. Detailed field-emission gun scanning electron microscopy (FESEM) images and small angle X-ray scattering (SAXS) data revealed parallel mesopores and ordered mesostructures. It is shown that the immobilized COOH groups are chemically accessible for acid-base reactions as well as copper adsorption. Immobilization of easily synthesized tailored carboxylic modified alkoxide precursors within mesoporous systems provides a unique chemical nanoenvironment within these ordered frameworks.

  12. Nucleic Acid i-Motif Structures in Analytical Chemistry.

    PubMed

    Alba, Joan Josep; Sadurní, Anna; Gargallo, Raimundo

    2016-09-02

    Under the appropriate experimental conditions of pH and temperature, cytosine-rich segments in DNA or RNA sequences may produce a characteristic folded structure known as an i-motif. Besides its potential role in vivo, which is still under investigation, this structure has attracted increasing interest in other fields due to its sharp, fast and reversible pH-driven conformational changes. This "on/off" switch at molecular level is being used in nanotechnology and analytical chemistry to develop nanomachines and sensors, respectively. This paper presents a review of the latest applications of this structure in the field of chemical analysis.

  13. Perfluoroalkyl acids and related chemistries Toxicokinetics and modes of action

    EPA Science Inventory

    The perfluoroalkyl acid salts (both carboxylates and sulfonates, hereafter designated as PFAAs) and their derivatives are important chemicals that have numerous consumer and industrial applications. However, recent discoveries that some of these compounds have global distribution...

  14. Ferroelectric based catalysis: Switchable surface chemistry

    NASA Astrophysics Data System (ADS)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2015-03-01

    We describe a new class of catalysts that uses an epitaxial monolayer of a transition metal oxide on a ferroelectric substrate. The ferroelectric polarization switches the surface chemistry between strongly adsorptive and strongly desorptive regimes, circumventing difficulties encountered on non-switchable catalytic surfaces where the Sabatier principle dictates a moderate surface-molecule interaction strength. This method is general and can, in principle, be applied to many reactions, and for each case the choice of the transition oxide monolayer can be optimized. Here, as a specific example, we show how simultaneous NOx direct decomposition (into N2 and O2) and CO oxidation can be achieved efficiently on CrO2 terminated PbTiO3, while circumventing oxygen (and sulfur) poisoning issues. One should note that NOx direct decomposition has been an open challenge in automotive emission control industry. Our method can expand the range of catalytically active elements to those which are not conventionally considered for catalysis and which are more economical, e.g., Cr (for NOx direct decomposition and CO oxidation) instead of canonical precious metal catalysts. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  15. Applications of azide-based bioorthogonal click chemistry in glycobiology.

    PubMed

    Zhang, Xiu; Zhang, Yan

    2013-06-19

    Click chemistry is a powerful chemical reaction with excellent bioorthogonality features: biocompatible, rapid and highly specific in biological environments. For glycobiology, bioorthogonal click chemistry has created a new method for glycan non-invasive imaging in living systems, selective metabolic engineering, and offered an elite chemical handle for biological manipulation and glycomics studies. Especially the [3 + 2] dipolar cycloadditions of azides with strained alkynes and the Staudinger ligation of azides and triarylphosphines have been widely used among the extant click reactions. This review focuses on the azide-based bioorthogonal click chemistry, describing the characteristics and development of these reactions, introducing some recent applications in glycobiology research, especially in glycan metabolic engineering, including glycan non-invasive imaging, glycomics studies and viral surface manipulation for drug discovery as well as other applications like activity-based protein profiling and carbohydrate microarrays.

  16. Heterogeneous chemistry in the troposphere: The nitric acid "renoxification"

    NASA Astrophysics Data System (ADS)

    Rivera-Figueroa, Armando M.

    2005-07-01

    The current observed discrepancy between the field and modeled NO x/HNO3 ratios suggests that chemistry that may affect the oxidative capacity of the atmosphere remains unidentified. We studied several heterogeneous reactions involving HNO3 and various atmospheric species (NO, CO, CH4 and SO2) proposed to reconcile these ratios. The BET surface area of several atmospherically available natural and anthropogenic surfaces was determined to evaluate the potential role in heterogeneous chemistry. The BET surface area of these surfaces was 3 to 5 orders of magnitude higher than the geometric surface area of the samples. Silica was chosen as the proxy surface of atmospherically available surfaces, and its interaction with water using a combination of FTIR and BET theory was studied. Hydroxylated silica absorbs ˜1.6 monolayers of water under ambient conditions (296 K, ˜50% RH). Using transmission FTIR, we monitored the reaction of surface-adsorbed HNO3 with gaseous CO, SO2, CH4 and NO. No reaction between HNO3 and CO, CH4 or SO2 was observed. Upper limits to the reaction probabilities (gammarxn ) were derived: ≤10-10 for CO and SO 2, and ≤10-12 for CH4. Therefore, these reactions are not expected to participate in "renoxification" in the boundary layer. However, the reaction of HNO3(ads) with NO does occur, producing gaseous NO2, with a lower limit for the reaction probability of gammaNO > (7 +/- 1) x 10-8 (2s) when only the surface area covered by HNO 3 was used. Molecular HNO3 was shown to be the reactive species instead of NO3-. This chemistry requires the presence of a thin water film on the surface. Recent studies by Kleffmann et al. (2004) reported to have an upper limit for the reaction probability for the HNO3-NO reaction of gamma NO→NO2 < 2.5 x 10-9. However, it is not clear whether the HNO3 was dissociated or the molecular form under their experimental conditions. The HNO3-NO reaction could be a significant means of "renoxification" of HNO3 on surfaces

  17. Boron and nucleic acid chemistries: merging the best of both worlds.

    PubMed

    Martin, Anthony R; Vasseur, Jean-Jacques; Smietana, Michael

    2013-07-07

    At the intersection of nucleic acid and boron chemistries lies a thriving world of possibilities. During the past decades, the merging of these research domains has led to fascinating discoveries in different fields ranging from material to medical sciences. In recent years the interplay of these two worlds has gained a lot of attention, as can be judged by the increasing number of articles in which boron and nucleic acids stand out for their potential medicinal, biotechnological or analytical applications. In this review, we present an outline of this crossroads by focusing on both the interaction of boronated compounds with nucleic acids and the modification of nucleic acids by boron containing moieties.

  18. Aluminum in acidic surface waters: chemistry, transport, and effects.

    PubMed Central

    Driscoll, C T

    1985-01-01

    Ecologically significant concentrations of Al have been reported in surface waters draining "acid-sensitive" watersheds that are receiving elevated inputs of acidic deposition. It has been hypothesized that mineral acids from atmospheric deposition have remobilized Al previously precipitated within the soil during soil development. This Al is then thought to be transported to adjacent surface waters. Dissolved mononuclear Al occurs as aquo Al, as well as OH-, F-, SO4(2-), and organic complexes. Although past investigations have often ignored non-hydroxide complexes of Al, it appears that organic and F complexes are the predominant forms of Al in dilute (low ionic strength) acidic surface waters. The concentration of inorganic forms of Al increases exponentially with decreases in solution pH. This response is similar to the theoretical pH dependent solubility of Al mineral phases. The concentration of organic forms of Al, however, is strongly correlated with variations in organic carbon concentration of surface waters rather than pH. Elevated concentrations of Al in dilute acidic waters are of interest because: Al is an important pH buffer; Al may influence the cycling of important elements like P, organic carbon, and trace metals; and Al is potentially toxic to aquatic organisms. An understanding of the aqueous speciation of Al is essential for an evaluation of these processes. PMID:3935428

  19. The Effectiveness of Predict-Observe-Explain Technique in Probing Students' Understanding about Acid-Base Chemistry: A Case for the Concepts of pH, pOH, and Strength

    ERIC Educational Resources Information Center

    Kala, Nesli; Yaman, Fatma; Ayas, Alipasa

    2013-01-01

    The present study describes high school students' conceptions about acids and bases in terms of pH, pOH, microscopic level, strength, and concentration. A total of 27 high school students participated in the study. The data was collected using 3 POE tasks and a semi-structured interview. The data analysis demonstrated that most of the students had…

  20. Amino Acid Complementarity: A Biochemical Exemplar of Stoichiometry for General and Health Sciences Chemistry

    ERIC Educational Resources Information Center

    Vitz, Ed

    2005-01-01

    The standard introduction to stoichiometry and simple exemplars can motivate students to learn the stoichiometric studies and the condensation reaction that occurs between amino acids to form the peptide bond. This topic can be integrated into general chemistry courses as an alternative to inclusion of a separate biochemistry course that could be…

  1. Chemistry For Kids: Pre-Chemistry Acid Rain Activities for Kids.

    ERIC Educational Resources Information Center

    Barrow, Lloyd H.

    1985-01-01

    Presents two activities on acid rain for students in intermediate grades. Materials needed and procedures used are included. Also describes "chemical magic" shows performed by high school students for sixth-grade students in seven elementary schools in Altus, Oklahoma. (JN)

  2. Chemistry: An Industry-Based Laboratory Manual (by John Kenkel)

    NASA Astrophysics Data System (ADS)

    Ballard, Sue K.

    2001-02-01

    Despite this concern, I find this to be an excellent lab manual for training potential chemistry-based laboratory technicians. It is apparent that a lot of thought, effort, and expertise went into producing a lab manual that students and teachers alike can appreciate. Buy it! You'll like it!

  3. Steering Siglec-Sialic Acid Interactions on Living Cells using Bioorthogonal Chemistry.

    PubMed

    Büll, Christian; Heise, Torben; van Hilten, Niek; Pijnenborg, Johan F A; Bloemendal, Victor R L J; Gerrits, Lotte; Kers-Rebel, Esther D; Ritschel, Tina; den Brok, Martijn H; Adema, Gosse J; Boltje, Thomas J

    2017-03-13

    Sialic acid sugars that terminate cell-surface glycans form the ligands for the sialic acid binding immunoglobulin-like lectin (Siglec) family, which are immunomodulatory receptors expressed by immune cells. Interactions between sialic acid and Siglecs regulate the immune system, and aberrations contribute to pathologies like autoimmunity and cancer. Sialic acid/Siglec interactions between living cells are difficult to study owing to a lack of specific tools. Here, we report a glycoengineering approach to remodel the sialic acids of living cells and their binding to Siglecs. Using bioorthogonal chemistry, a library of cells with more than sixty different sialic acid modifications was generated that showed dramatically increased binding toward the different Siglec family members. Rational design reduced cross-reactivity and led to the discovery of three selective Siglec-5/14 ligands. Furthermore, glycoengineered cells carrying sialic acid ligands for Siglec-3 dampened the activation of Siglec-3(+) monocytic cells through the NF-κB and IRF pathways.

  4. Click chemistry in peptide-based drug design.

    PubMed

    Li, Huiyuan; Aneja, Rachna; Chaiken, Irwin

    2013-08-16

    Click chemistry is an efficient and chemoselective synthetic method for coupling molecular fragments under mild reaction conditions. Since the advent in 2001 of methods to improve stereochemical conservation, the click chemistry approach has been broadly used to construct diverse chemotypes in both chemical and biological fields. In this review, we discuss the application of click chemistry in peptide-based drug design. We highlight how triazoles formed by click reactions have been used for mimicking peptide and disulfide bonds, building secondary structural components of peptides, linking functional groups together, and bioconjugation. The progress made in this field opens the way for synthetic approaches to convert peptides with promising functional leads into structure-minimized and more stable forms.

  5. Click Chemistry in Peptide-Based Drug Design

    PubMed Central

    Li, Huiyuan; Aneja, Rachna; Chaiken, Irwin

    2014-01-01

    Click chemistry is an efficient and chemoselective synthetic method for coupling molecular fragments under mild reaction conditions. Since the advent in 2001 of methods to improve stereochemical conservation, the click chemistry approach has been broadly used to construct diverse chemotypes in both chemical and biological fields. In this review, we discuss the application of click chemistry in peptide-based drug design. We highlight how triazoles formed by click reactions have been used for mimicking peptide and disulfide bonds, building secondary structural components of peptides, linking functional groups together, and bioconjugation. The progress made in this field opens the way for synthetic approaches to convert peptides with promising functional leads into structure-minimized and more stable forms. PMID:23959192

  6. Physical chemistry of nucleic acids and their complexes.

    PubMed

    Ghirlando, Rodolfo; Felsenfeld, Gary

    2013-12-01

    Studies of the physical properties of nucleic acids began almost immediately following the discovery of the DNA structure. Early investigations focused on the stability and specificity of multi-strand polynucleotide complexes, then gradually on their interaction with other molecules, particularly proteins. As molecular and structural biology expanded to provide detailed information about biochemical mechanisms, physical studies eventually acquired the additional constraint that they should be relevant to functioning biological systems. We describe work in our laboratory that began with investigations of relatively simple questions about the role of electrostatic interactions in the stabilization of multi-strand nucleic acid structures, and evolved to studies of chromatin structure in vitro and within the nucleus.

  7. Atmospheric chemistry of carboxylic acids: microbial implication versus photochemistry

    NASA Astrophysics Data System (ADS)

    Vaïtilingom, M.; Charbouillot, T.; Deguillaume, L.; Maisonobe, R.; Parazols, M.; Amato, P.; Sancelme, M.; Delort, A.-M.

    2011-02-01

    Clouds are multiphasic atmospheric systems in which the dissolved organic compounds, dominated by carboxylic acids, are subject to multiple chemical transformations in the aqueous phase. Among them, solar radiation, by generating hydroxyl radicals (•OH), is considered as the main catalyzer of the reactivity of organic species in clouds. We investigated to which extent the active biomass existing in cloud water represents an alternative route to the chemical reactivity of carboxylic acids. Pure cultures of seventeen bacterial strains (Arthrobacter, Bacillus, Clavibacter, Frigoribacterium, Pseudomonas, Sphingomonas and Rhodococcus), previously isolated from cloud water and representative of the viable community of clouds were first individually incubated in two artificial bulk cloud water solutions at 17 °C and 5 °C. These solutions mimicked the chemical composition of cloud water from "marine" and "continental" air masses, and contained the major carboxylic acids existing in the cloud water (i.e. acetate, formate, succinate and oxalate). The concentrations of these carboxylic compounds were monitored over time and biodegradation rates were determined. In average, they ranged from 2 ×10-19 for succinate to 1 × 10-18 mol cell-1 s-1 for formate at 17 °C and from 4 × 10-20 for succinate to 6 × 10-19 mol cell-1 s-1 for formate at 5 °C, with no significant difference between "marine" and "continental" media. In parallel, irradiation experiments were also conducted in these two artificial media to compare biodegradation and photodegradation of carboxylic compounds. To complete this comparison, the photodegradation rates of carboxylic acids by •OH radicals were calculated from literature data. Inferred estimations suggested a significant participation of microbes to the transformation of carboxylic acids in cloud water, particularly for acetate and succinate (up to 90%). Furthermore, a natural cloud water sample was incubated (including its indigenous microflora

  8. Effect of Hydrofluoric Acid Etching Time on Titanium Topography, Chemistry, Wettability, and Cell Adhesion

    PubMed Central

    Zahran, R.; Rosales Leal, J. I.; Rodríguez Valverde, M. A.; Cabrerizo Vílchez, M. A.

    2016-01-01

    Titanium implant surface etching has proven an effective method to enhance cell attachment. Despite the frequent use of hydrofluoric (HF) acid, many questions remain unresolved, including the optimal etching time and its effect on surface and biological properties. The objective of this study was to investigate the effect of HF acid etching time on Ti topography, surface chemistry, wettability, and cell adhesion. These data are useful to design improved acid treatment and obtain an improved cell response. The surface topography, chemistry, dynamic wetting, and cell adhesiveness of polished Ti surfaces were evaluated after treatment with HF acid solution for 0, 2; 3, 5, 7, or 10 min, revealing a time-dependent effect of HF acid on their topography, chemistry, and wetting. Roughness and wetting increased with longer etching time except at 10 min, when roughness increased but wetness decreased. Skewness became negative after etching and kurtosis tended to 3 with longer etching time. Highest cell adhesion was achieved after 5–7 min of etching time. Wetting and cell adhesion were reduced on the highly rough surfaces obtained after 10-min etching time. PMID:27824875

  9. New Trends in Chemistry Teaching, Volume 2.

    ERIC Educational Resources Information Center

    Cartmell, E.

    This second volume of UNESCO's series on New Trends in Chemistry Teaching presents papers originally published during 1966 and 1967 in leading chemistry-teaching periodicals of the world. The papers have been grouped in sections - structure, energetics and kinetics, acids and bases, organic chemistry, electrochemistry, chemistry and industry,…

  10. Acid mist and ozone effects on the leaf chemistry of two western conifer species.

    PubMed

    Westman, W E; Temple, P J

    1989-01-01

    Seedlings of Jeffrey pine (Pinus jeffreyi) and giant sequoia (Sequoiadendron gigantea) were more susceptible to leaf chemical changes following exposure to acid mist (pH 3.4-2.0) or acid mist/ozone combinations, than to ozone alone (0.1-0.2 microl/litre), when plants were exposed to alternating doses of these pollutants for 6-9 weeks. Under acid mist treatment, leaves exhibited higher levels of nitrogen and sulfur, two elements applied in acid mist. In addition, levels of foliar sodium, and, in the case of giant sequia, potassium, as well, increased under acid mist treatment. Iron and manganese were also mobilized, resulting in significant increases in these elements in pine, and decreases in manganese in giant sequoia foliage. The acid treatment also reduced chlorophyll b concentrations in pine, and, to a less significant extent, in giant sequoia. Calcium, magnesium, barium and strontium were differentially accumulated in giant sequoia compared to Jeffrey pine. Under acid mist treatment, all of these elements (except strontium) declined in concentration in giant sequoia, with calcium showing the most significant trend. The more extensive changes in leaf chemistry induced by acid mist are consistent with earlier observations of significant changes in spectral reflectance of these seedlings after 3 weeks of fumigation. Limited foliage samples collected from these two species in 1985 and 1986 in Sequoia/Kings Canyon National Parks in the southern Sierra Nevada do not in themselves indicate any clearcut or severe effects of ozone alone on leaf chemistry of these species, but a mild influence of nitrate-laden acid deposition, possibly in combination with ozone, is consistent with the rise in nitrogen and lignin levels in Jeffrey pine on sites observed to have moderate visible injury symptoms. No firm conclusions about effects of pollutants on leaf chemistry in these field sites is possible without further study.

  11. [Computational chemistry in structure-based drug design].

    PubMed

    Cao, Ran; Li, Wei; Sun, Han-Zi; Zhou, Yu; Huang, Niu

    2013-07-01

    Today, the understanding of the sequence and structure of biologically relevant targets is growing rapidly and researchers from many disciplines, physics and computational science in particular, are making significant contributions to modern biology and drug discovery. However, it remains challenging to rationally design small molecular ligands with desired biological characteristics based on the structural information of the drug targets, which demands more accurate calculation of ligand binding free-energy. With the rapid advances in computer power and extensive efforts in algorithm development, physics-based computational chemistry approaches have played more important roles in structure-based drug design. Here we reviewed the newly developed computational chemistry methods in structure-based drug design as well as the elegant applications, including binding-site druggability assessment, large scale virtual screening of chemical database, and lead compound optimization. Importantly, here we address the current bottlenecks and propose practical solutions.

  12. Effectiveness of Case-Based Learning Instruction on Pre-Service Teachers' Chemistry Motivation and Attitudes toward Chemistry

    ERIC Educational Resources Information Center

    Çam, Aylin; Geban, Ömer

    2017-01-01

    Background: The development of primary pre-service teachers' chemistry motivation and attitudes toward chemistry were examined in order to develop their science literacy using case-based learning. Students' ideas were emphasized, real-life situations were discussed, and students could share their ideas and knowledge with peers; as a result,…

  13. Computer-Based Learning in Chemistry Classes

    ERIC Educational Resources Information Center

    Pietzner, Verena

    2014-01-01

    Currently not many people would doubt that computers play an essential role in both public and private life in many countries. However, somewhat surprisingly, evidence of computer use is difficult to find in German state schools although other countries have managed to implement computer-based teaching and learning in their schools. This paper…

  14. Metal-free pincer ligand chemistry polycationic phosphonium Lewis acids.

    PubMed

    Szkop, Kevin M; Stephan, Douglas W

    2017-03-07

    Oxidation of 2,6-bis(diphenylphosphine)methyl pyridine with MeO3SCF3, yields the dication [2,6-(CH2PMePh2)2C5H3N][CF3SO3]22, while subsequent treatment with two equivalents of [K(THF)n][B(C6F5)4] (n = 1.3-1.5) afforded [2,6-(CH2PMePh2)2C5H3N][B(C6F5)4]23. Analogous treatment using XeF2 afforded 2,6-(CH2PF2Ph2)2C5H3N 4, while subsequent fluoride abstractions afford the corresponding [BF4], [CF3SO3] and [B(C6F5)4] salts, 5-7, respectively. Compound 4 reacts with an excess of MeO3SCF3 to give [2,6-(CH2PF2Ph2)2C5H3N(CH3)][CF3SO3] 8 while subsequent reaction with [Et3Si·2C7H8][B(C6F5)4] gave the related tricationic species, 9. The Lewis acidity of these di- and triphosphonium cations 3, 7 and 9 was examined and their utility as Lewis acid catalysts was assessed in the dimerization of 1,1-diphenylethylene, the hydrodefluorination of 1-fluoroadamantane, and the dehydrocoupling of phenol and silane.

  15. Going Beyond, Going Further: The Preparation of Acid-Base Titration Curves.

    ERIC Educational Resources Information Center

    McClendon, Michael

    1984-01-01

    Background information, list of materials needed, and procedures used are provided for a simple technique for generating mechanically plotted acid-base titration curves. The method is suitable for second-year high school chemistry students. (JN)

  16. Developing an Internet-Based Chemistry Class

    NASA Astrophysics Data System (ADS)

    Patterson, Mary Jane

    2000-05-01

    With the increasing popularity of Internet-based classes, more faculty are being asked to develop them (1). In Texas, the Virtual College of Texas (http://www.vct.org) even provides a forum that allows community colleges to advertise their distance-learning classes, and it paves the way for a college to offer a distance-learning class from any other college in the state. The two colleges simply work out a Memorandum of Understanding, mutually deciding how to administer the class, divide fees, set enrollment limits, among other details. While some classes are easily adapted to an Internet format, lab sciences raise a number of issues that must be tackled before a quality course can be developed in this new medium. I will raise some of those issues and offer a few possibilities.

  17. Structure-based classification and ontology in chemistry

    PubMed Central

    2012-01-01

    Background Recent years have seen an explosion in the availability of data in the chemistry domain. With this information explosion, however, retrieving relevant results from the available information, and organising those results, become even harder problems. Computational processing is essential to filter and organise the available resources so as to better facilitate the work of scientists. Ontologies encode expert domain knowledge in a hierarchically organised machine-processable format. One such ontology for the chemical domain is ChEBI. ChEBI provides a classification of chemicals based on their structural features and a role or activity-based classification. An example of a structure-based class is 'pentacyclic compound' (compounds containing five-ring structures), while an example of a role-based class is 'analgesic', since many different chemicals can act as analgesics without sharing structural features. Structure-based classification in chemistry exploits elegant regularities and symmetries in the underlying chemical domain. As yet, there has been neither a systematic analysis of the types of structural classification in use in chemistry nor a comparison to the capabilities of available technologies. Results We analyze the different categories of structural classes in chemistry, presenting a list of patterns for features found in class definitions. We compare these patterns of class definition to tools which allow for automation of hierarchy construction within cheminformatics and within logic-based ontology technology, going into detail in the latter case with respect to the expressive capabilities of the Web Ontology Language and recent extensions for modelling structured objects. Finally we discuss the relationships and interactions between cheminformatics approaches and logic-based approaches. Conclusion Systems that perform intelligent reasoning tasks on chemistry data require a diverse set of underlying computational utilities including algorithmic

  18. Synthesis and cytotoxicity of triterpenoids derived from betulin and betulinic acid via click chemistry.

    PubMed

    Shi, Wei; Tang, Ning; Yan, Wei-Dong

    2015-01-01

    In this study, a series of triazole substituted betulin and betulinic acid derivatives was designed and synthesized via click chemistry at C-30 position. Eighteen target compounds were evaluated in vitro for their antitumor activities against leukemia cell-line HL-60. Seventeen compounds have not reported before. The cytotoxic experiment showed that most of betulinic acid derived triazoles have higher cytotoxic profile than betulinic acid. Among them, compound 30-[4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl] betulinic acid (7b) showed the best IC50 value (1.3 μM) against leukemia cell-line HL-60 (eight- to ninefold higher potency than betulinic acid).

  19. The impact of acid treatment on soilwater chemistry at the Humex site

    SciTech Connect

    Vogt, R.D.; Ranneklev, S.B.; Mykkelbost, T.C. )

    1994-01-01

    The effects of acid treatment on soil water dissolved organic carbon (DOC) and inorganic chemistry are being monitored at the Humic Lake Acidification Experiment (HUMEX) in western Norway. The HUMEX project involves artificial acidification of half of a dystrophic lake and the corresponding drainage basin. Soil water chemistry data were collected from 30 monitoring lysimeters and 130 grid lysimeters. The samples from the monitoring lysimeters were collected before and, for a period of two years, after the onset of acid treatment. Operationally-defined functional fractions of DOC showed that hydrophilic (HPI) and hydrophobic (HPO) acids account for 60% to 90% of the DOC. In soils rich in DOC, the HPO acids were dominant, whereas in mineral soil horizons low in DOC, the HPI acid fractions were highest. The amount of DOC relative to labile aluminum and iron may determine the HPO/HPI acid ratio. The sulphate concentration has increased more in the treated than in the reference side. Coincident decreases in DOC and organically complexes aluminum (Al[sub 0]) concentrations were observed for surface histosol locations. The temporal and spatial variations in c(Al[sub 0]) were mainly explained by variation in c(DOC). 26 refs., 5 figs., 3 tabs.

  20. 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…

  1. Chemistry in Microfluidic Channels

    ERIC Educational Resources Information Center

    Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.

    2011-01-01

    General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of…

  2. The EPA Comptox Chemistry Dashboard: A Web-Based Data ...

    EPA Pesticide Factsheets

    The U.S. Environmental Protection Agency (EPA) Computational Toxicology Program integrates advances in biology, chemistry, and computer science to help prioritize chemicals for further research based on potential human health risks. This work involves computational and data driven approaches that integrate chemistry, exposure and biological data. As an outcome of these efforts the National Center for Computational Toxicology (NCCT) has measured, assembled and delivered an enormous quantity and diversity of data for the environmental sciences including high-throughput in vitro screening data, in vivo and functional use data, exposure models and chemical databases with associated properties. A series of software applications and databases have been produced over the past decade to deliver these data but recent developments have focused on the development of a new software architecture that assembles the resources into a single platform. A new web application, the CompTox Chemistry Dashboard provides access to data associated with ~720,000 chemical substances. These data include experimental and predicted physicochemical property data, bioassay screening data associated with the ToxCast program, product and functional use information and a myriad of related data of value to environmental scientists. The dashboard provides chemical-based searching based on chemical names, synonyms and CAS Registry Numbers. Flexible search capabilities allow for chemical identificati

  3. Fines classification based on sensitivity to pore-fluid chemistry

    USGS Publications Warehouse

    Jang, Junbong; Santamarina, J. Carlos

    2016-01-01

    The 75-μm particle size is used to discriminate between fine and coarse grains. Further analysis of fine grains is typically based on the plasticity chart. Whereas pore-fluid-chemistry-dependent soil response is a salient and distinguishing characteristic of fine grains, pore-fluid chemistry is not addressed in current classification systems. Liquid limits obtained with electrically contrasting pore fluids (deionized water, 2-M NaCl brine, and kerosene) are combined to define the soil “electrical sensitivity.” Liquid limit and electrical sensitivity can be effectively used to classify fine grains according to their fluid-soil response into no-, low-, intermediate-, or high-plasticity fine grains of low, intermediate, or high electrical sensitivity. The proposed methodology benefits from the accumulated experience with liquid limit in the field and addresses the needs of a broader range of geotechnical engineering problems.

  4. Sunlight-initiated Chemistry of Aqueous Pyruvic Acid: Building Complexity in the Origin of Life

    NASA Astrophysics Data System (ADS)

    Griffith, Elizabeth C.; Shoemaker, Richard K.; Vaida, Veronica

    2013-10-01

    Coupling chemical reactions to an energy source is a necessary step in the origin of life. Here, we utilize UV photons provided by a simulated sun to activate aqueous pyruvic acid and subsequently prompt chemical reactions mimicking some of the functions of modern metabolism. Pyruvic acid is interesting in a prebiotic context due to its prevalence in modern metabolism and its abiotic availability on early Earth. Here, pyruvic acid (CH3COCOOH, a C3 molecule) photochemically reacts to produce more complex molecules containing four or more carbon atoms. Acetoin (CH3CHOHCOCH3), a C4 molecule and a modern bacterial metabolite, is produced in this chemistry as well as lactic acid (CH3CHOHCOOH), a molecule which, when coupled with other abiotic chemical reaction pathways, can provide a regeneration pathway for pyruvic acid. This chemistry is discussed in the context of plausible environments on early Earth such as near the ocean surface and atmospheric aerosol particles. These environments allow for combination and exchange of reactants and products of other reaction environments (such as shallow hydrothermal vents). The result could be a contribution to the steady increase in chemical complexity requisite in the origin of life.

  5. Acid mist and ozone effects on the leaf chemistry of two western conifer species

    NASA Technical Reports Server (NTRS)

    Westman, Walter E.; Temple, Patrick J.

    1989-01-01

    The effects of ozone and acid-mist exposures on the leaf chemistry of Jeffrey pine and giant sequoia seedlings grown in filtered-air greenhouses were investigated. Acid-mist treatments (pH 4.1, 3.4, 2.7, or 2.0) were administered for 3 h, and ozone exposures (0, 0.10, and 0.20 microliter/liter), which followed acid-mist treatments, for 4 h, each for three days a week for six to nine weeks. It was found that seedlings were more susceptible to acid-mist and acid mist/ozone combinations, than to ozone alone. Acid mist treatment resulted in higher levels of nitrogen and sulfur (both present in acid mist) as well as Na. Leaves of giant sequoia exhibited increased K and decreased Mn, while Jeffrey pine showed increases in Fe and Mn. In sequoia leaves, concentrations of Ca, Mg, and Ba decreased. Acid treatment also reduced chlorophyll b concentrations in both conifer species. Extensive changes induced by acid mist are consistent with earlier observations of changes in spectral reflectance of conifer seedlings observed after three weeks of fumigation.

  6. Development and Assessment of Green, Research-Based Instructional Materials for the General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Cacciatore, Kristen L.

    2010-01-01

    This research entails integrating two novel approaches for enriching student learning in chemistry into the context of the general chemistry laboratory. The first is a pedagogical approach based on research in cognitive science and the second is the green chemistry philosophy. Research has shown that inquiry-based approaches are effective in…

  7. Changes in stream chemistry and biology in response to reduced levels of acid deposition during 1987-2003 in the Neversink River Basin, Catskill Mountains

    USGS Publications Warehouse

    Burns, Douglas A.; Riva-Murray, K.; Bode, R.W.; Passy, S.

    2008-01-01

    Atmospheric acid deposition has decreased in the northeastern United States since the 1970s, resulting in modest increases in pH, acid-neutralizing capacity (ANC), and decreases in inorganic monomeric aluminum (AlIM) concentrations since stream chemistry monitoring began in the 1980s in the acid-sensitive upper Neversink River basin in the Catskill Mountains of New York. Stream pH has increased by 0.01 units/year during 1987-2003 at three sites in the Neversink basin as determined by Seasonal Kendall trend analysis. In light of this observed decrease in stream acidity, we sampled 12 stream sites within the Neversink River watershed for water chemistry, macroinvertebrates, fish, and periphytic diatoms in 2003 to compare with a similar data set collected in 1987. Metrics and indices that reflect sensitivity to stream acidity were developed with these biological data to determine whether changes in stream biota over the intervening 16 years parallel those of stream chemistry. Statistical comparisons of data on stream chemistry and an acid biological assessment profile (Acid BAP) derived from invertebrate data showed no significant differences between the two years. For pH and ANC, however, values in 2003 were generally lower than those in 1987; this difference likely resulted from higher streamflow in summer 2003. Despite these likely flow-induced changes in summer 2003, an ordination and cluster analysis of macroinvertebrate taxa based on the Acid BAP indicated that the most acidic sites in the upstream half of the East Branch Neversink River form a statistically significant separate cluster consistent with less acidic stream conditions. This analysis is consistent with limited recovery of invertebrate species in the most acidic reaches of the river, but will require additional improvement in stream chemistry before a stronger conclusion can be drawn. Data on the fish and periphytic diatom communities in 2003 indicate that slimy sculpin had not extended their habitat

  8. New Perspectives on Context-Based Chemistry Education: Using a Dialectical Sociocultural Approach to View Teaching and Learning

    ERIC Educational Resources Information Center

    King, Donna

    2012-01-01

    Context-based chemistry education aims to improve student interest and motivation in chemistry by connecting canonical chemistry concepts with real-world contexts. Implementation of context-based chemistry programmes began 20 years ago in an attempt to make the learning of chemistry meaningful for students. This paper reviews such programmes…

  9. Component-based integration of chemistry and optimization software.

    PubMed

    Kenny, Joseph P; Benson, Steven J; Alexeev, Yuri; Sarich, Jason; Janssen, Curtis L; McInnes, Lois Curfman; Krishnan, Manojkumar; Nieplocha, Jarek; Jurrus, Elizabeth; Fahlstrom, Carl; Windus, Theresa L

    2004-11-15

    Typical scientific software designs make rigid assumptions regarding programming language and data structures, frustrating software interoperability and scientific collaboration. Component-based software engineering is an emerging approach to managing the increasing complexity of scientific software. Component technology facilitates code interoperability and reuse. Through the adoption of methodology and tools developed by the Common Component Architecture Forum, we have developed a component architecture for molecular structure optimization. Using the NWChem and Massively Parallel Quantum Chemistry packages, we have produced chemistry components that provide capacity for energy and energy derivative evaluation. We have constructed geometry optimization applications by integrating the Toolkit for Advanced Optimization, Portable Extensible Toolkit for Scientific Computation, and Global Arrays packages, which provide optimization and linear algebra capabilities. We present a brief overview of the component development process and a description of abstract interfaces for chemical optimizations. The components conforming to these abstract interfaces allow the construction of applications using different chemistry and mathematics packages interchangeably. Initial numerical results for the component software demonstrate good performance, and highlight potential research enabled by this platform.

  10. Impact of mitigation strategies on acid sulfate soil chemistry and microbial community.

    PubMed

    Wu, Xiaofen; Sten, Pekka; Engblom, Sten; Nowak, Pawel; Österholm, Peter; Dopson, Mark

    2015-09-01

    Potential acid sulfate soils contain reduced iron sulfides that if oxidized, can cause significant environmental damage by releasing large amounts of acid and metals. This study examines metal and acid release as well as the microbial community capable of catalyzing metal sulfide oxidation after treating acid sulfate soil with calcium carbonate (CaCO3) or calcium hydroxide (Ca(OH)2). Leaching tests of acid sulfate soil samples were carried out in the laboratory. The pH of the leachate during the initial flushing with water lay between 3.8 and 4.4 suggesting that the jarosite/schwertmannite equilibrium controls the solution chemistry. However, the pH increased to circa 6 after treatment with CaCO3 suspension and circa 12 after introducing Ca(OH)2 solution. 16S rRNA gene sequences amplified from community DNA extracted from the untreated and both CaCO3 and Ca(OH)2 treated acid sulfate soils were most similar to bacteria (69.1% to 85.7%) and archaea (95.4% to 100%) previously identified from acid and metal contaminated environments. These species included a Thiomonas cuprina-like and an Acidocella-like bacteria as well as a Ferroplasma acidiphilum-like archeon. Although the CaCO3 and Ca(OH)2 treatments did not decrease the proportion of microorganisms capable of accelerating acid and metal release, the chemical effects of the treatments suggested their reduced activity.

  11. Using the Logarithmic Concentration Diagram, Log "C", to Teach Acid-Base Equilibrium

    ERIC Educational Resources Information Center

    Kovac, Jeffrey

    2012-01-01

    Acid-base equilibrium is one of the most important and most challenging topics in a typical general chemistry course. This article introduces an alternative to the algebraic approach generally used in textbooks, the graphical log "C" method. Log "C" diagrams provide conceptual insight into the behavior of aqueous acid-base systems and allow…

  12. High School Students' Understanding of Acid-Base Concepts: An Ongoing Challenge for Teachers

    ERIC Educational Resources Information Center

    Damanhuri, Muhd Ibrahim Muhamad; Treagust, David F.; Won, Mihye; Chandrasegaran, A. L.

    2016-01-01

    Using a quantitative case study design, the "Acids-Bases Chemistry Achievement Test" ("ABCAT") was developed to evaluate the extent to which students in Malaysian secondary schools achieved the intended curriculum on acid-base concepts. Responses were obtained from 260 Form 5 (Grade 11) students from five schools to initially…

  13. Evaluation of modeled cloud chemistry mechanism against laboratory irradiation experiments: The HxOy/iron/carboxylic acid chemical system

    NASA Astrophysics Data System (ADS)

    Long, Yoann; Charbouillot, Tiffany; Brigante, Marcello; Mailhot, Gilles; Delort, Anne-Marie; Chaumerliac, Nadine; Deguillaume, Laurent

    2013-10-01

    Currently, cloud chemistry models are including more detailed and explicit multiphase mechanisms based on laboratory experiments that determine such values as kinetic constants, stability constants of complexes and hydration constants. However, these models are still subject to many uncertainties related to the aqueous chemical mechanism they used. Particularly, the role of oxidants such as iron and hydrogen peroxide in the oxidative capacity of the cloud aqueous phase has typically never been validated against laboratory experimental data. To fill this gap, we adapted the M2C2 model (Model of Multiphase Cloud Chemistry) to simulate irradiation experiments on synthetic aqueous solutions under controlled conditions (e.g., pH, temperature, light intensity) and for actual cloud water samples. Various chemical compounds that purportedly contribute to the oxidative budget in cloud water (i.e., iron, oxidants, such as hydrogen peroxide: H2O2) were considered. Organic compounds (oxalic, formic and acetic acids) were taken into account as target species because they have the potential to form iron complexes and are good indicators of the oxidative capacity of the cloud aqueous phase via their oxidation in this medium. The range of concentrations for all of the chemical compounds evaluated was representative of in situ measurements. Numerical outputs were compared with experimental data that consisted of a time evolution of the concentrations of the target species. The chemical mechanism in the model describing the “oxidative engine” of the HxOy/iron (HxOy = H2O2, HO2rad /O2rad - and HOrad ) chemical system was consistent with laboratory measurements. Thus, the degradation of the carboxylic acids evaluated was closely reproduced by the model. However, photolysis of the Fe(C2O4)+ complex needs to be considered in cloud chemistry models for polluted conditions (i.e., acidic pH) to correctly reproduce oxalic acid degradation. We also show that iron and formic acid lead to

  14. Project-based learning in the secondary chemistry classroom

    NASA Astrophysics Data System (ADS)

    Crane, Elizabeth L.

    This study investigated the use of project-based learning (PBL) in a high school chemistry classroom. PBL encourages the use of projects, which promote continual learning, rather than a summative project at the end of a unit after the learning has already been done. Along with implementing PBL, the study also incorporated many of the strategies included in the broader strategy known as Assessment for Learning (AfL), which stresses developing assessments that are part of the learning process rather than simply a measurement of the amount of learning that has occurred upon completion of a unit. The hypothesis of this research was that PBL would increase student comprehension and motivation as measured through pre and post-test data and a student survey. The new project-based unit required students to research and present the properties and structures of elements and how we use them. The expectation was that this approach would engage students with the material, the computer modeling would allow for more concrete visualization of structures and the project-based format would allow students to become more invested in their own learning. This study provided evidence to support the hypothesis that the implementation of project-based learning, supported by formative assessment and other assessment for learning strategies, will improve student comprehension and motivation in the secondary chemistry classroom.

  15. A Thematic Review of Studies into the Effectiveness of Context-Based Chemistry Curricula

    NASA Astrophysics Data System (ADS)

    Ültay, Neslihan; Çalık, Muammer

    2012-12-01

    Context-based chemistry education aims at making connections between real life and the scientific content of chemistry courses. The purpose of this study was to evaluate context-based chemistry studies. In looking for the context-based chemistry studies, the authors entered the keywords `context-based', `contextual learning' and `chemistry education' in well-known databases (i.e. Academic Search Complete, Education Research Complete, ERIC, Springer LINK Contemporary). Further, in case the computer search by key words may have missed a rather substantial part of the important literature in the area, the authors also conducted a hand search of the related journals. To present a detailed thematic review of context-based chemistry studies, a matrix was used to summarize the findings by focusing on insights derived from the related studies. The matrix incorporates the following themes: needs, aims, methodologies, general knowledge claims, and implications for teaching and learning, implications for curriculum development and suggestions for future research. The general knowledge claims investigated in this paper were: (a) positive effects of the context-based chemistry studies; (b) caveats, both are examined in terms of students' attitudes and students' understanding/cognition. Implications were investigated for practice in context- based chemistry studies, for future research in context- based chemistry studies, and for curriculum developers in context- based chemistry studies. Teachers of context-based courses claimed that the application of the context-based learning approach in chemistry education improved students' motivation and interest in the subject. This seems to have generated an increase in the number of the students who wish to continue chemistry education at higher levels. However, despite the fact that the majority of the studies have reported advantages of context-based chemistry studies, some of them have also referred to pitfalls, i.e. dominant

  16. Evolution of water chemistry in natural acidic environments in Yangmingshan, Taiwan.

    PubMed

    Ezoe, Yuka; Lin, Cheng-Huang; Noto, Masami; Watanabe, Yoshihiro; Yoshimura, Kazuhisa

    2002-08-01

    In Yangmingshan National Park, located in the northern part of the Taiwan Island, there is a very rare area where fish (Channa asiatica) live in spite of acid environments. The origin of the acid in local acid ponds and rivers and the evolution of the water chemistry are discussed on the basis of sulfur stable isotope ratios and chemical equilibria. One of the sources of the acid is sulfuric acid, which is derived from the oxidation of hydrogen sulfide in volcanic gas gushing out from fumaroles around the area and from acid deposition supplied from Taipei City. It is also derived from the oxidation of pyrite: the sulfur stable isotope ratios of delta 34S of +1@1000 to +4@1000 (relative to CDT) of sulfate in acid pond waters (pH 3-4) could be related to those of hydrogen sulfide in volcanic gas, pyrite in local pond sediments and soils, and sulfate in rain water. One acid source is sulfuric and hydrochloric acids arising in springs from geothermal activity: the delta 34S values were characterised by +13@1000 to +17@1000 sulfate-S, which was provided by a disproportionation reaction of sulfur dioxide in the depths. Another acid source could be the oxidation of iron(II). Under acidic conditions, the water-rock reaction gives rise to high concentrations of aluminium and iron. While flowing down surface streams, iron(II) is oxidised to iron(III) and then hydrolysed to cause further acidification under oxic conditions. The concentrations of iron and aluminium are controlled by redox and dissolution equilibria.

  17. Effect of backbone chemistry on hybridization thermodynamics of oligonucleic acids: a coarse-grained molecular dynamics simulation study.

    PubMed

    Ghobadi, Ahmadreza F; Jayaraman, Arthi

    2016-02-28

    In this paper we study how varying oligonucleic acid backbone chemistry affects the hybridization/melting thermodynamics of oligonucleic acids. We first describe the coarse-grained (CG) model with tunable parameters that we developed to enable the study of both naturally occurring oligonucleic acids, such as DNA, and their chemically-modified analogues, such as peptide nucleic acids (PNAs) and locked nucleic acids (LNAs). The DNA melting curves obtained using such a CG model and molecular dynamics simulations in an implicit solvent and with explicit ions match with the melting curves obtained using the empirical nearest-neighbor models. We use these CG simulations to then elucidate the effect of backbone flexibility, charge, and nucleobase spacing along the backbone on the melting curves, potential energy and conformational entropy change upon hybridization and base-pair hydrogen bond residence time. We find that increasing backbone flexibility decreases duplex thermal stability and melting temperature mainly due to increased conformational entropy loss upon hybridization. Removing charges from the backbone enhances duplex thermal stability due to the elimination of electrostatic repulsion and as a result a larger energetic gain upon hybridization. Lastly, increasing nucleobase spacing decreases duplex thermal stability due to decreasing stacking interactions that are important for duplex stability.

  18. A Collaborative, Wiki-Based Organic Chemistry Project Incorporating Free Chemistry Software on the Web

    ERIC Educational Resources Information Center

    Evans, Michael J.; Moore, Jeffrey S.

    2011-01-01

    In recent years, postsecondary instructors have recognized the potential of wikis to transform the way students learn in a collaborative environment. However, few instructors have embraced in-depth student use of chemistry software for the creation of interactive chemistry content on the Web. Using currently available software, students are able…

  19. Development and Assessment of a Chemistry-Based Computer Video Game as a Learning Tool

    ERIC Educational Resources Information Center

    Martinez-Hernandez, Kermin Joel

    2010-01-01

    The chemistry-based computer video game is a multidisciplinary collaboration between chemistry and computer graphics and technology fields developed to explore the use of video games as a possible learning tool. This innovative approach aims to integrate elements of commercial video game and authentic chemistry context environments into a learning…

  20. Student Use of Web-Based Tutorial Materials and Understanding of Chemistry Concepts

    ERIC Educational Resources Information Center

    Donovan, William; Nakhleh, Mary

    2007-01-01

    This article reports the findings of Phase II of our study of student use of web-based tutorial materials for general chemistry and student understanding of chemistry concepts. We have found that students who use the web site valued the aspects of visualization of chemistry concepts and availability of materials online. In our analysis of student…

  1. In situ visualization of newly synthesized proteins in environmental microbes using amino acid tagging and click chemistry

    PubMed Central

    Hatzenpichler, Roland; Scheller, Silvan; Tavormina, Patricia L; Babin, Brett M; Tirrell, David A; Orphan, Victoria J

    2014-01-01

    Here we describe the application of a new click chemistry method for fluorescent tracking of protein synthesis in individual microorganisms within environmental samples. This technique, termed bioorthogonal non-canonical amino acid tagging (BONCAT), is based on the in vivo incorporation of the non-canonical amino acid L-azidohomoalanine (AHA), a surrogate for l-methionine, followed by fluorescent labelling of AHA-containing cellular proteins by azide-alkyne click chemistry. BONCAT was evaluated with a range of phylogenetically and physiologically diverse archaeal and bacterial pure cultures and enrichments, and used to visualize translationally active cells within complex environmental samples including an oral biofilm, freshwater and anoxic sediment. We also developed combined assays that couple BONCAT with ribosomal RNA (rRNA)-targeted fluorescence in situ hybridization (FISH), enabling a direct link between taxonomic identity and translational activity. Using a methanotrophic enrichment culture incubated under different conditions, we demonstrate the potential of BONCAT-FISH to study microbial physiology in situ. A direct comparison of anabolic activity using BONCAT and stable isotope labelling by nano-scale secondary ion mass spectrometry (15NH3 assimilation) for individual cells within a sediment-sourced enrichment culture showed concordance between AHA-positive cells and 15N enrichment. BONCAT-FISH offers a fast, inexpensive and straightforward fluorescence microscopy method for studying the in situ activity of environmental microbes on a single-cell level. PMID:24571640

  2. Bioorthogonal click chemistry to assay mu-opioid receptor palmitoylation using 15-hexadecynoic acid and immunoprecipitation

    PubMed Central

    Ebersole, Brittany; Petko, Jessica; Levenson, Robert

    2014-01-01

    We have developed a modification of bioorthogonal click chemistry to assay the palmitoylation of cellular proteins. This assay utilizes 15-hexadecynoic acid (15-HDYA) as a chemical probe in combination with protein immunoprecipitation using magnetic beads in order to detect S-palmitoylation of proteins of interest. Here we demonstrate the utility of this approach for the mu-opioid receptor (MOR), a GPCR responsible for mediating the analgesic and addictive properties of most clinically relevant opioid agonist drugs. This technique provides a rapid, non-isotopic, and efficient method to assay the palmitoylation status of a variety of cellular proteins including most GPCRs. PMID:24463015

  3. A National Science Standards-Based Study of Web-Based Inquiry in Chemistry

    NASA Astrophysics Data System (ADS)

    Shive, Louise E.; Bodzin, Alec M.; Cates, Ward Mitchell

    2004-07-01

    From a sample of 137 chemistry-related Web sites in the public domain, 17 were identified as Web-based inquiry activities (WBIs). Identification was made using an instrument developed in accord with national science standards. A multi-pass unanimous consensus analysis was used to examine how the 17 WBIs reflected the five essential elements of inquiry and to classify the WBIs accordingly. Instructional and design features of chemistry-related WBIs are described.

  4. The Mismatch between Students' Mental Models of Acids/Bases and Their Sources and Their Teacher's Anticipations Thereof

    ERIC Educational Resources Information Center

    Lin, Jing-Wen; Chiu, Mei-Hung

    2010-01-01

    The aim of this study is to compare the characteristics and sources of students' mental models of acids and bases with a teacher's anticipations and, based on this comparison, to explore some possible explanations why motivated students might fail to learn from a subject-knowledgeable chemistry teacher. The study involves a chemistry teacher and…

  5. The Synthesis and Isolation of N-Tert-Butyl-2-Phenylsuccinamic Acid and N-Tert-Butyl-3-Phenylsuccinamic Acid: An Undergraduate Organic Chemistry Laboratory Experiment

    ERIC Educational Resources Information Center

    Cesare, Victor; Sadarangani, Ishwar; Rollins, Janet; Costello, Dennis

    2004-01-01

    The facile, high yielding synthesis of phenylsuccinamic acids is described and one of these syntheses, the reaction of phenylsuccinic anhydride with tert-butylamine, is successfully modified and adapted for use in the second-semester organic chemistry laboratory at St. John's University. Succinamic acids are compounds that contain both the amide…

  6. Membrane-based microextraction techniques in analytical chemistry: A review.

    PubMed

    Carasek, Eduardo; Merib, Josias

    2015-06-23

    The use of membrane-based sample preparation techniques in analytical chemistry has gained growing attention from the scientific community since the development of miniaturized sample preparation procedures in the 1990s. The use of membranes makes the microextraction procedures more stable, allowing the determination of analytes in complex and "dirty" samples. This review describes some characteristics of classical membrane-based microextraction techniques (membrane-protected solid-phase microextraction, hollow-fiber liquid-phase microextraction and hollow-fiber renewal liquid membrane) as well as some alternative configurations (thin film and electromembrane extraction) used successfully for the determination of different analytes in a large variety of matrices, some critical points regarding each technique are highlighted.

  7. Chemistry resolved kinetic flow modeling of TATB based explosives

    NASA Astrophysics Data System (ADS)

    Vitello, Peter; Fried, Laurence E.; William, Howard; Levesque, George; Souers, P. Clark

    2012-03-01

    Detonation waves in insensitive, TATB-based explosives are believed to have multiple time scale regimes. The initial burn rate of such explosives has a sub-microsecond time scale. However, significant late-time slow release in energy is believed to occur due to diffusion limited growth of carbon. In the intermediate time scale concentrations of product species likely change from being in equilibrium to being kinetic rate controlled. We use the thermo-chemical code CHEETAH linked to an ALE hydrodynamics code to model detonations. We term our model chemistry resolved kinetic flow, since CHEETAH tracks the time dependent concentrations of individual species in the detonation wave and calculates EOS values based on the concentrations. We present here two variants of our new rate model and comparison with hot, ambient, and cold experimental data for PBX 9502.

  8. Chemistry Resolved Kinetic Flow Modeling of TATB Based Explosives

    SciTech Connect

    Vitello, P A; Fried, L E; Howard, W M; Levesque, G; Souers, P C

    2011-07-21

    Detonation waves in insensitive, TATB based explosives are believed to have multi-time scale regimes. The initial burn rate of such explosives has a sub-microsecond time scale. However, significant late-time slow release in energy is believed to occur due to diffusion limited growth of carbon. In the intermediate time scale concentrations of product species likely change from being in equilibrium to being kinetic rate controlled. They use the thermo-chemical code CHEETAH linked to an ALE hydrodynamics code to model detonations. They term their model chemistry resolved kinetic flow as CHEETAH tracks the time dependent concentrations of individual species in the detonation wave and calculates EOS values based on the concentrations. A HE-validation suite of model simulations compared to experiments at ambient, hot, and cold temperatures has been developed. They present here a new rate model and comparison with experimental data.

  9. Molecular basis of fatty acid selectivity in the zDHHC family of S-acyltransferases revealed by click chemistry

    PubMed Central

    Greaves, Jennifer; Munro, Kevin R.; Davidson, Stuart C.; Riviere, Matthieu; Wojno, Justyna; Smith, Terry K.; Tomkinson, Nicholas C. O.; Chamberlain, Luke H.

    2017-01-01

    S-acylation is a major posttranslational modification, catalyzed by the zinc finger DHHC domain containing (zDHHC) enzyme family. S-acylated proteins can be modified by different fatty acids; however, very little is known about how zDHHC enzymes contribute to acyl chain heterogeneity. Here, we used fatty acid-azide/alkyne labeling of mammalian cells, showing their transformation into acyl-CoAs and subsequent click chemistry-based detection, to demonstrate that zDHHC enzymes have marked differences in their fatty acid selectivity. This difference in selectivity was apparent even for highly related enzymes, such as zDHHC3 and zDHHC7, which displayed a marked difference in their ability to use C18:0 acyl-CoA as a substrate. Furthermore, we identified isoleucine-182 in transmembrane domain 3 of zDHHC3 as a key determinant in limiting the use of longer chain acyl-CoAs by this enzyme. This study uncovered differences in the fatty acid selectivity profiles of cellular zDHHC enzymes and mapped molecular determinants governing this selectivity. PMID:28167757

  10. 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.

  11. Understanding prebiotic chemistry through the analysis of extraterrestrial amino acids and nucleobases in meteorites.

    PubMed

    Burton, Aaron S; Stern, Jennifer C; Elsila, Jamie E; Glavin, Daniel P; Dworkin, Jason P

    2012-08-21

    The discoveries of amino acids of extraterrestrial origin in many meteorites over the last 50 years have revolutionized the Astrobiology field. A variety of non-terrestrial amino acids similar to those found in life on Earth have been detected in meteorites. A few amino acids have even been found with chiral excesses, suggesting that meteorites could have contributed to the origin of homochirality in life on Earth. In addition to amino acids, which have been productively studied for years, sugar-like molecules, activated phosphates, and nucleobases have also been determined to be indigenous to numerous meteorites. Because these molecules are essential for life as we know it, and meteorites have been delivering them to the Earth since accretion, it is plausible that the origin(s) of life on Earth were aided by extraterrestrially-synthesized molecules. Understanding the origins of life on Earth guides our search for life elsewhere, helping to answer the question of whether biology is unique to Earth. This tutorial review focuses on meteoritic amino acids and nucleobases, exploring modern analytical methods and possible formation mechanisms. We will also discuss the unique window that meteorites provide into the chemistry that preceded life on Earth, a chemical record we do not have access to on Earth due to geologic recycling of rocks and the pervasiveness of biology across the planet. Finally, we will address the future of meteorite research, including asteroid sample return missions.

  12. Understanding Prebiotic Chemistry Through the Analysis of Extraterrestrial Amino Acids and Nucleobases in Meteorites

    NASA Technical Reports Server (NTRS)

    Burton, Aaron S.; Stern, Jennifer C.; Elsila, Jamie E.; Glavin, Daniel P.; Dworkin, Jason P.

    2012-01-01

    The discoveries of amino acids of extraterrestrial origin in many meteorites over the last 50 years have revolutionized the Astrobiology field. A variety of non-terrestrial amino acids similar to those found in life on Earth have been detected in meteorites. A few amino acids have even been found with chiral excesses, suggesting that meteorites could have contributed to the origin of homochirality in life on Earth. In addition to amino acids, which have been productively studied for years, sugar-like molecules, activated phosphates, and nucleobases have also been determined to be indigenous to numerous meteorites. Because these molecules are essential for life as we know it, and meteorites have been delivering them to the Earth since accretion, it is plausible that the origines) of life on Earth were aided by extrataterrestrially-synthesized molecules. Understanding the origins of life on Earth guides our search for life elsewhere, helping to answer the question of whether biology is unique to Earth. This tutorial focuses on meteoritic amino acids and nucleobases, exploring modern analytical methods and possible formation mechanisms. We will also discuss the unique window that meteorites provide into the chemistry that preceded life on Earth, a chemical record we do not have access to on Earth due to geologic recycling of rocks and the pervasiveness of biology across the planet. Finally. we will address the future of meteorite research, including asteroid sample return missions.

  13. Reevaluation of Neptunium-Nitric Acid Radiation Chemistry by Multiscale Modeling.

    PubMed

    Horne, G P; Grimes, T S; Mincher, B J; Mezyk, S P

    2016-12-15

    Multiscale modeling has been used to quantitatively reevaluate the radiation chemistry of neptunium in a range of aerated nitric acid solutions (0.1-6.0 mol dm(-3)). Exact calculation of initial radiolytic yields accounting for changes in radiation track chemistry was found to be crucial for reproducing experimental data. The γ irradiation induces changes in the Np(VI)/Np(V) oxidation-state distribution, predominantly driven by reactions involving HNO2, H2O2, NO2(•), and NO3(•) from the radiolysis of aqueous nitric acid. Oxidation of Np(V) by NO3(•) (k = 8.1 × 10(8) dm(3) mol(-1) s(-1)) provides the initial increase in Np(VI) concentration, while also delaying net reduction of Np(VI) by consuming HNO2. Reduction of Np(VI) is dominated by thermal reactions with HNO2 (k = 0.7-73 dm(3) mol(-1) s(-1)) and H2O2 (k = 1.9 dm(3) mol(-1) s(-1)). A steady state is eventually established once the concentration of Np(V) is sufficiently high to be oxidized by NO2(•) (k = 2.4 × 10(2)-3.1 × 10(4) dm(3) mol(-1) s(-1)). An additional thermal oxidation reaction between Np(V) and HNO3 (k = 2.0 × 10(3) dm(3) mol(-1) s(-1)) is required for nitric acid concentrations >4.0 mol dm(-3). For 0.1 mol dm(-3) HNO3, the rate of Np(VI) reduction is in excess of that which can be accounted for by radiolytic product mass balance, suggesting the existence of a catalytic-acid-dependent reduction process.

  14. Bioorthogonal Click Chemistry-Based Synthetic Cell Glue.

    PubMed

    Koo, Heebeom; Choi, Myunghwan; Kim, Eunha; Hahn, Sei Kwang; Weissleder, Ralph; Yun, Seok Hyun

    2015-12-22

    Artificial methods of cell adhesion can be effective in building functional cell complexes in vitro, but methods for in vivo use are currently lacking. Here, a chemical cell glue based on bioorthogonal click chemistry with high stability and robustness is introduced. Tetrazine (Tz) and trans-cyclooctene (TCO) conjugated to the cell surface form covalent bonds between cells within 10 min in aqueous conditions. Glued, homogeneous, or heterogeneous cell pairs remain viable and stably attached in a microfluidic flow channel at a shear stress of 20 dyn cm(-2) . Upon intravenous injection of assembled Jurkat T cells into live mice, fluorescence microscopy shows the trafficking of cell pairs in circulation and their infiltration into lung tissues. These results demonstrate the promising potential of chemically glued cell pairs for various applications ranging from delivering therapeutic cells to studying cell-cell interactions in vivo.

  15. The Effect of Web-Based Project Applications on Students' Attitudes towards Chemistry

    ERIC Educational Resources Information Center

    Morgil, Inci; Gungor Seyhan, Hatice; Ural Alsan, Evrim; Temel, Senar

    2008-01-01

    Students perform intensive web-based applications during their education. One of these is project-based application. In this study, the effect of web based project applications on students' attitudes towards chemistry has been investigated. 42 students attending Hacettepe University, Faculty of Education, and Department of Chemistry Education have…

  16. Photon and Water Mediated Sulfur Oxide and Acid Chemistry in the Atmosphere of Venus

    NASA Astrophysics Data System (ADS)

    Kroll, Jay A.; Vaida, Veronica

    2014-06-01

    Sulfur compounds have been observed in the atmospheres of a number of planetary bodies in our solar system including Venus, Earth, Mars, Io, Europa, and Callisto. The global cloud cover on Venus located at an altitude between 50 and 80 kilometers is composed primarily of sulfuric acid (H_2SO_4) and water. Planetary photochemical models have attempted to explain observations of sulfuric acid and sulfur oxides with significant discrepancies remaining between models and observation. In particular, high SO_2 mixing ratios are observed above 90 km which exceed model predictions by orders of magnitude. Work recently done in the Vaida lab has shown red light can drive photochemistry through overtone pumping for acids like H_2SO_4 and has been successful in explaining much of the sulfur chemistry in Earth's atmosphere. Water can have a number of interesting effects such as catalysis, suppression, and anti-catalysis of thermal and photochemical processes. We investigate the role of water complexes in the hydration of sulfur oxides and dehydration of sulfur acids and present spectroscopic studies to document such effects. We investigate these reactions using FTIR and UV/Vis spectroscopy and will report on our findings.

  17. Reductive alkylation of hyaluronic acid for the synthesis of biocompatible hydrogels by click chemistry.

    PubMed

    Huerta-Angeles, Gloria; Němcová, Miroslava; Příkopová, Eva; Šmejkalová, Daniela; Pravda, Martin; Kučera, Lukáš; Velebný, Vladimír

    2012-11-06

    Hyaluronan (HA) based hydrogels have been synthesized combining chemical modification of the polysaccharide by partial oxidation, reductive amination and 'click chemistry'. HA was oxidized by 4-acetamido-TEMPO-mediated reaction, using sodium hypochlorite as primary oxidant and NaBr in buffered pH, so that the produced aldehyde moieties (hemiacetals) were trapped in situ by adding primary amines containing azide or alkyne-terminal groups. The structure of the reaction products, oxidized-HA and primary amines bonded to HA, was elucidated using 2D NMR spectroscopy. SEC-MALLS analysis of the modified substrates showed a negligible degradation of the polysaccharide using this procedure. Furthermore, azido- and alkynyl derivatives underwent cross-linking by click chemistry into hydrogels, which were characterized by NMR, FT-IR, swelling degree and mechanical properties. Possible application of the material as scaffold for tissue engineering was tested by seeding and proliferation of chondrocytes for up to 15 days.

  18. Tetrazine-based chemistry for nitrite determination in a paper microfluidic device.

    PubMed

    Ortiz-Gomez, Inmaculada; Ortega-Muñoz, Mariano; Salinas-Castillo, Alfonso; Álvarez-Bermejo, José Antonio; Ariza-Avidad, Maria; de Orbe-Payá, Ignacio; Santoyo-Gonzalez, Francisco; Capitan-Vallvey, Luis Fermin

    2016-11-01

    We present a new chemistry to determine nitrites implemented in a microfluidic paper-based analytical device (µPAD). The device is fabricated in cellulose paper with a sample reception area and three replicate detection areas with recognition chemistry immobilized by adsorption. The method involves the use of nitrite in an acid medium reaction to generate nitrous acid, which produces the oxidation of s-dihydrotetrazine: 1,2-dihydro-3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazine (DHBPTz), which change the detection zone from colorless to pink. We used a digital camera and smartphone for the quantitative analysis of nitrite with the color coordinate S of the HSV color space as the analytical parameter. Parameters such as concentration and volume of s-dihydrotetrazine, pH, sample volume and reaction time were studied. The detection limit for this method is 1.30µM nitrite. To estimate the selectivity of the method an interference study of common ions in water samples was performed. The procedure was applied to natural water and compared with reference procedures.

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

    PubMed

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

    2013-11-07

    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.

  20. Aqueous chemistry of lithium hydroxide and boric acid and corrosion of Zircaloy-4 and Zr-2.5Nb alloys

    SciTech Connect

    Ramasubramanian, N.; Balakrishnan, P.V.

    1994-12-31

    The chemistry of the aqueous solution, surface chemistry of zirconium oxide (ZrO{sub 2}), and the physical structure of the corrosion film have to be considered for an understanding of the mechanism of corrosion of zirconium alloys in aqueous solutions. Based on information available in all these areas, the authors are proposing a model for oxide growth on Zircaloy-4 fuel cladding and Zr-2.5Nb pressure tube material, in lithium hydroxide (LiOH) solutions with and without added boric acid (H{sub 3}BO{sub 3}). Corrosion exposures were at 360 C and were short term of four-day duration. Concentration of lithium covered the range 0.7 to 3,500 ppm and boron was added at 300, 600 and 1,200 ppm. Weight gain, Fourier Transform InfraRed (FTIR) spectroscopy, and Secondary ion Mass Spectrometry (SIMS) were used to characterize the oxide films. Potentiodynamic polarization measurements were made in separate tests at 315 C. The chemistry of LiOH-H{sub 3}BO{sub 3} system at 300 to 360 C was evaluated from the ionization constants of water, LiOH, and H{sub 3}BO{sub 3}. There is no simple relationship between pH and corrosion. In the absence of boron acceleration in corrosion, in these short-term tests, is observed at concentrations >350 ppm Li for Zircaloy-4 and at >60 ppm Li for Zr-2.5Nb. According to the model proposed for oxide growth, the corrosion behavior can be classified into two categories: (1) growth of post-transition type films under acceleration conditions where solution had access into the oxide and (2) growth of pre-transition films under non-acceleration conditions where the solution had not gained access into the oxide.

  1. Magnetic hyaluronic acid nanospheres via aqueous Diels-Alder chemistry to deliver dexamethasone for adipose tissue engineering.

    PubMed

    Jia, Yang; Fan, Ming; Chen, Huinan; Miao, Yuting; Xing, Lian; Jiang, Bohong; Cheng, Qifan; Liu, Dongwei; Bao, Weikang; Qian, Bin; Wang, Jionglu; Xing, Xiaodong; Tan, Huaping; Ling, Zhonghua; Chen, Yong

    2015-11-15

    Biopolymer-based nanospheres have great potential in the field of drug delivery and tissue regenerative medicine. In this work, we present a flexible way to conjugate a magnetic hyaluronic acid (HA) nanosphere system that are capable of vectoring delivery of adipogenic factor, e.g. dexamethasone, for adipose tissue engineering. Conjugation of nanospheres was established by aqueous Diels-Alder chemistry between furan and maleimide of HA derivatives. Simultaneously, a furan functionalized dexamethasone peptide, GQPGK, was synthesized and covalently immobilized into the nanospheres. The magnetic HA nanospheres were fabricated by encapsulating super-paramagnetic iron oxide nanoparticles, which exhibited quick magnetic sensitivity. The aqueous Diels-Alder chemistry made nanospheres high binding efficiency of dexamethasone, and the vectoring delivery of dexamethasone could be easily controlled by a external magnetic field. The potential application of the magnetic HA nanospheres on vectoring delivery of adipogenic factor was confirmed by co-culture of human adipose-derived stem cells (ASCs). In vitro cytotoxicity tests demonstrated that incorporation of dexamethasone into magnetic HA nanospheres showed high efficiency to promote ASCs viabilities, in particular under a magnetic field, which suggested a promising future for adipose regeneration applications.

  2. Beginning Chemistry Can Be Relevant

    ERIC Educational Resources Information Center

    Corwin, James F.

    1971-01-01

    Reviews ways of applying laboratory work in general and analytical chemistry to supermarket products. Describes ways water and air pollution analysis can illustrate acid-base reactions, redox reactions, precipitimetry, and colorimetry. (PR)

  3. Organic Experiments for Introductory Chemistry.

    ERIC Educational Resources Information Center

    Rayner-Canham, Geoff

    1985-01-01

    Describes test-tube organic chemistry procedures (using comparatively safe reagents) for the beginning student. These procedures are used to: examine differences between saturated and unsaturated hydrocarbons; compare structural isomers; and compare organic and inorganic acids and bases. (DH)

  4. 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…

  5. Instructional Misconceptions in Acid-Base Equilibria: An Analysis from a History and Philosophy of Science Perspective

    ERIC Educational Resources Information Center

    Kousathana, Margarita; Demerouti, Margarita; Tsaparlis, Georgios

    2005-01-01

    The implications of history and philosophy of chemistry are explored in the context of chemical models. Models and modeling provide the context through which epistemological aspects of chemistry can be promoted. In this work, the development of ideas and models about acids and bases (with emphasis on the Arrhenius, the Bronsted-Lowry, and the…

  6. Attitudes toward a Simulation Based Chemistry Curriculum for Nursing Students.

    ERIC Educational Resources Information Center

    Dori, Yehudit

    Chemistry anxiety exists among nursing students as well as other allied health professions. The causes for this anxiety may be attributed to three variables. Chemistry: (1) is perceived as difficult; (2) involves a multitude of facts; and (3) is not connected to reality. A curriculum with a simulation format has been developed to help Israeli…

  7. Construction of Protein-Based Biosensors Using Ligand-Directed Chemistry for Detecting Analyte Binding.

    PubMed

    Yamaura, Kei; Kiyonaka, Shigeki; Hamachi, Itaru

    2017-01-01

    Protein-based fluorescent biosensors are powerful tools for quantitative detection of biomolecules or drugs with high sensitivity under physiological conditions. However, conventional methods for construction of biosensors require structural data with high resolution or amino acid sequence information in most cases, which hampers applicability of this method to structurally complicated receptor proteins. To sidestep such limitations, we recently developed a new method that employs ligand-directed chemistry coupled with a bimolecular fluorescence quenching and recovery system, which enabled the conversion of various kinds of membrane-bound receptors to "turn-on" type fluorescent sensors. Here, we describe a protocol for construction of "turn-on" type fluorescent biosensors based on the GABAA receptor which permits quantitative analysis of the ligand affinity.

  8. ADIBO-based "click" chemistry for diagnostic peptide micro-array fabrication: physicochemical and assay characteristics.

    PubMed

    Prim, Denis; Rebeaud, Fabien; Cosandey, Vincent; Marti, Roger; Passeraub, Philippe; Pfeifer, Marc E

    2013-08-16

    Several azide-derivatized and fluorescently-labeled peptides were immobilized on azadibenzocyclooctyne (ADIBO)-activated slide surfaces via a strain-promoted alkyne-azide cycloaddition (SPAAC) reaction revealing excellent immobilization kinetics, good spot homogeneities and reproducible fluorescence signal intensities. A myc-peptide micro-array immunoassay showed an antibody limit-of-detection (LOD) superior to a microtiter plate-based ELISA. Bovine serum albumin (BSA) and dextran covalently attached via "click" chemistry more efficiently reduced non-specific binding (NSB) of fluorescently-labeled IgG to the microarray surface in comparison to immobilized hexanoic acid and various types of polyethylene glycol (PEG) derivatives. Confirmation of these findings via further studies with other proteins and serum components could open up new possibilities for human sample and microarray platform-based molecular diagnostic tests.

  9. Aqueous Dispersions of Silica Stabilized with Oleic Acid Obtained by Green Chemistry

    PubMed Central

    Nistor, Cristina Lavinia; Ianchis, Raluca; Ghiurea, Marius; Nicolae, Cristian-Andi; Spataru, Catalin-Ilie; Culita, Daniela Cristina; Pandele Cusu, Jeanina; Fruth, Victor; Oancea, Florin; Donescu, Dan

    2016-01-01

    The present study describes for the first time the synthesis of silica nanoparticles starting from sodium silicate and oleic acid (OLA). The interactions between OLA and sodium silicate require an optimal OLA/OLANa molar ratio able to generate vesicles that can stabilize silica particles obtained by the sol-gel process of sodium silicate. The optimal molar ratio of OLA/OLANa can be ensured by a proper selection of OLA and respectively of sodium silicate concentration. The titration of sodium silicate with OLA revealed a stabilization phenomenon of silica/OLA vesicles and the dependence between their average size and reagent’s molar ratio. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) measurements emphasized the successful synthesis of silica nanoparticles starting from renewable materials, in mild condition of green chemistry. By grafting octadecyltrimethoxysilane on the initial silica particles, an increased interaction between silica particles and the OLA/OLANa complex was achieved. This interaction between the oleyl and octadecyl chains resulted in the formation of stable gel-like aqueous systems. Subsequently, olive oil and an oleophylic red dye were solubilized in these stable aqueous systems. This great dispersing capacity of oleosoluble compounds opens new perspectives for future green chemistry applications. After the removal of water and of the organic chains by thermal treatment, mesoporous silica was obtained.

  10. Effects of iron on arsenic speciation and redox chemistry in acid mine water

    USGS Publications Warehouse

    Bednar, A.J.; Garbarino, J.R.; Ranville, J.F.; Wildeman, T.R.

    2005-01-01

    Concern about arsenic is increasing throughout the world, including areas of the United States. Elevated levels of arsenic above current drinking-water regulations in ground and surface water can be the result of purely natural phenomena, but often are due to anthropogenic activities, such as mining and agriculture. The current study correlates arsenic speciation in acid mine drainage and mining-influenced water with the important water-chemistry properties Eh, pH, and iron(III) concentration. The results show that arsenic speciation is generally in equilibrium with iron chemistry in low pH AMD, which is often not the case in other natural-water matrices. High pH mine waters and groundwater do not always hold to the redox predictions as well as low pH AMD samples. The oxidation and precipitation of oxyhydroxides deplete iron from some systems, and also affect arsenite and arsenate concentrations through sorption processes. ?? 2004 Elsevier B.V. All rights reserved.

  11. A New Project-Based Lab for Undergraduate Environmental and Analytical Chemistry

    ERIC Educational Resources Information Center

    Adami, Gianpiero

    2006-01-01

    A new project-based lab was developed for third year undergraduate chemistry students based on real world applications. The experience suggests that the total analytical procedure (TAP) project offers a stimulating alternative for delivering science skills and developing a greater interest for analytical chemistry and environmental sciences and…

  12. Context-Based and Conventional Approaches to Teaching Chemistry: Comparing Teachers' Views

    ERIC Educational Resources Information Center

    Bennett, Judith; Grasel, Cornelia; Parchmann, Ilka; Waddington, David

    2005-01-01

    The study explores teachers' experiences of teaching a context-based chemistry course, "Salters Advanced Chemistry", as compared with teachers of a conventional course. Second, main factors that appear to influence decisions over whether or not to adopt context-based courses are investigated. Two hundred and twenty-two teachers' views of a…

  13. Explaining the Spatial Variability in Stream Acid Buffering Chemistry and Aquatic Biota in the Neversink River Watershed, Catskill Mountains, New York State

    NASA Astrophysics Data System (ADS)

    Harpold, A. A.; Walter, M. T.

    2009-12-01

    The Neversink River Watershed (NRW) originates at the highest point in the Catskill Mountains and is sensitive to changing patterns in acidic deposition, precipitation, and air temperature. Despite reductions in fossil fuel emission since the Clean Air Act, past acidic deposition has accelerated the leaching of cations from the soil and reduced the stores of base cations necessary for buffering stream acidity. The goal of this study was to investigate connections between different watershed ‘features’ and the apparently complex spatial patterns of stream buffering chemistry (specifically, acid neutralizing capacity ANC and Ca concentrations) and aquatic biota (macroinvertebrate and fish populations). The ten nested NRW watersheds (2.0 km^2 to 176.0 km^2) have relatively homogeneous bedrock geology, forested cover, and soil series; therefore, we hypothesized that differing distributions of hydrological flowpaths between the watersheds control the variability in stream buffering chemistry and aquatic biota. However because the flowpath distributions are not directly measurable, this study used step-wise linear regression to develop relationships between watershed ‘features’ and buffering chemistry. The regression results showed that the mean ratio of precipitation to stream runoff (or runoff ratio) from twenty non-winter storm events explained more than 81% of the variability in mean summer ANC and Ca concentrations. The results also suggested that steeper (higher mean slope) more channelized watersheds (larger drainage density) are more susceptible to stream acidity and negative impacts on biota. A simple linear relationship (using no discharge or water chemistry measurements) was able to explain buffering chemistry and aquatic biota populations in 17 additional NRW watersheds (0.3 km^2 to 160.0 km^2), including 60-80% of the variability in macroinvertebrate populations (EPT richness and BAP) and 50-60% of the variability in fish density and species richness

  14. Chemistry laboratory safety manual available

    NASA Technical Reports Server (NTRS)

    Elsbrock, R. G.

    1968-01-01

    Chemistry laboratory safety manual outlines safe practices for handling hazardous chemicals and chemistry laboratory equipment. Included are discussions of chemical hazards relating to fire, health, explosion, safety equipment and procedures for certain laboratory techniques and manipulations involving glassware, vacuum equipment, acids, bases, and volatile solvents.

  15. Molnets: An Artificial Chemistry Based on Neural Networks

    NASA Technical Reports Server (NTRS)

    Colombano, Silvano; Luk, Johnny; Segovia-Juarez, Jose L.; Lohn, Jason; Clancy, Daniel (Technical Monitor)

    2002-01-01

    The fundamental problem in the evolution of matter is to understand how structure-function relationships are formed and increase in complexity from the molecular level all the way to a genetic system. We have created a system where structure-function relationships arise naturally and without the need of ad hoc function assignments to given structures. The idea was inspired by neural networks, where the structure of the net embodies specific computational properties. In this system networks interact with other networks to create connections between the inputs of one net and the outputs of another. The newly created net then recomputes its own synaptic weights, based on anti-hebbian rules. As a result some connections may be cut, and multiple nets can emerge as products of a 'reaction'. The idea is to study emergent reaction behaviors, based on simple rules that constitute a pseudophysics of the system. These simple rules are parameterized to produce behaviors that emulate chemical reactions. We find that these simple rules show a gradual increase in the size and complexity of molecules. We have been building a virtual artificial chemistry laboratory for discovering interesting reactions and for testing further ideas on the evolution of primitive molecules. Some of these ideas include the potential effect of membranes and selective diffusion according to molecular size.

  16. Chemistry Resolved Kinetic Flow Modeling of TATB Based Explosives

    NASA Astrophysics Data System (ADS)

    Vitello, Peter; Fried, Lawrence; Howard, Mike; Levesque, George; Souers, Clark

    2011-06-01

    Detonation waves in insensitive, TATB based explosives are believed to have multi-time scale regimes. The initial burn rate of such explosives has a sub-microsecond time scale. However, significant late-time slow release in energy is believed to occur due to diffusion limited growth of carbon. In the intermediate time scale concentrations of product species likely change from being in equilibrium to being kinetic rate controlled. We use the thermo-chemical code CHEETAH linked to ALE hydrodynamics codes to model detonations. We term our model chemistry resolved kinetic flow as CHEETAH tracks the time dependent concentrations of individual species in the detonation wave and calculate EOS values based on the concentrations. A validation suite of model simulations compared to recent high fidelity metal push experiments at ambient and cold temperatures has been developed. We present here a study of multi-time scale kinetic rate effects for these experiments. Prepared by LLNL under Contract DE-AC52-07NA27344.

  17. The Meteorology and Chemistry of High Nitric-Acid Episodes at the South Pole

    NASA Astrophysics Data System (ADS)

    Neff, William; Davis, Douglas

    2016-04-01

    Between 1998 and 2007, a series of field experiments carried out at the South Pole and with aircraft over a wider area revealed a very chemically active boundary layer overlying the east Antarctic ice sheet during the Austral summer. An early discovery was unexpectedly high concentrations of nitric acid (NO) at the South Pole. These were argued to be a result of the UV pholoysis of reactive nitrogen in surface and/or near-surface snow followed by subsequent confinement and non-linear HOx/NOx chemistry within a thin stable atmospheric boundary layer. The concentrations of NO also demonstrated daily, intraseasonal, as well as interannual variability as seen in the four field programs. This paper seeks to elucidate the interplay of large-to-small scale meteorology and chemistry at the South Pole that leads to highly variable NO concentrations and to examine boundary layer depth effects on NO in years when no direct measurements were available, in particular during the latest field program in 2006-2007. The importance of the South Pole is that it, unlike other high-latitude sites, has no diurnal cycle to disturb the evolution of the mostly stable boundary layer and its physics and chemistry. In the spring, as the solar elevation angle increases, nitrate photolysis rates increase. At the same time, the stratospheric vortex warms and with its breakup, the total column ozone increases leading to decreased photolysis rates. In addition, following the formation of the thermal tropopause in early spring, the tropospheric circulation over Antarctica changes dramatically, affecting the transport and dominant source regions for warm air and clouds arriving at the South Pole. The timing of the final warming ranged from early-November to mid-December for the four field experiment years. During the 30 days prior to the final increase in column ozone, as the thermal tropopause forms (~100 hPa), the winds at 300 hPa become bimodal, either along the eastern side of the Weddell Sea

  18. A National Science Standards-Based Study of Web-Based Inquiry in Chemistry

    ERIC Educational Resources Information Center

    Shive, Louise; Bodzin, Alec M.; Cates, Ward Mitchell

    2004-01-01

    Inquiry-based teaching and learning and technology integration are integral parts of the National Science Education Standards ad AAAA Project 2061 Benchmarks for Science Literacy. It is found that there are very few chemistry WBIs in the public domain, and the WBIs found are with a limited scope and content coverage and so the need for extensive…

  19. Discovery and development of natural product-derived chemotherapeutic agents based on a medicinal chemistry approach.

    PubMed

    Lee, Kuo-Hsiung

    2010-03-26

    Medicinal plants have long been an excellent source of pharmaceutical agents. Accordingly, the long-term objectives of the author's research program are to discover and design new chemotherapeutic agents based on plant-derived compound leads by using a medicinal chemistry approach, which is a combination of chemistry and biology. Different examples of promising bioactive natural products and their synthetic analogues, including sesquiterpene lactones, quassinoids, naphthoquinones, phenylquinolones, dithiophenediones, neo-tanshinlactone, tylophorine, suksdorfin, DCK, and DCP, will be presented with respect to their discovery and preclinical development as potential clinical trial candidates. Research approaches include bioactivity- or mechanism of action-directed isolation and characterization of active compounds, rational drug design-based modification and analogue synthesis, and structure-activity relationship and mechanism of action studies. Current clinical trial agents discovered by the Natural Products Research Laboratories, University of North Carolina, include bevirimat (dimethyl succinyl betulinic acid), which is now in phase IIb trials for treating AIDS. Bevirimat is also the first in a new class of HIV drug candidates called "maturation inhibitors". In addition, an etoposide analogue, GL-331, progressed to anticancer phase II clinical trials, and the curcumin analogue JC-9 is in phase II clinical trials for treating acne and in development for trials against prostate cancer. The discovery and development of these clinical trial candidates will also be discussed.

  20. Examining the Impact of Nitrous Acid Chemistry on Ozone and PM over the Pearl River Delta Region

    EPA Science Inventory

    The impact of nitrous acid (HONO) chemistry on regional ozone and particulate matter in Pearl River Delta region was investigated using the community multiscale air quality (CMAQ) modeling system and the CB05 mechanism. Model simulations were conducted for a ten-day period in Oct...

  1. Ionic Strength Effect on the Rate of Reduction of Hexacyanoferrate (III) by Ascorbic Acid: A Physical Chemistry Laboratory Experiment.

    ERIC Educational Resources Information Center

    Watkins, Kenneth W.; Olson, June A.

    1980-01-01

    Describes a physical chemistry experiment that allows students to test the effect of ionic strength on the rates of a reaction between ions. The reduction of hexacyanoferrate III by ascorbic acid is detailed. Comparisons with the iodine clock reaction are made. (CS)

  2. Development and Implementation of a Simple, Engaging Acid Rain Neutralization Experiment and Corresponding Animated Instructional Video for Introductory Chemistry Students

    ERIC Educational Resources Information Center

    Rand, Danielle; Yennie, Craig J.; Lynch, Patrick; Lowry, Gregory; Budarz, James; Zhu, Wenlei; Wang, Li-Qiong

    2016-01-01

    Here we describe an acid rain neutralization laboratory experiment and its corresponding instructional video. This experiment has been developed and implemented for use in the teaching laboratory of a large introductory chemistry course at Brown University. It provides a contextually relevant example to introduce beginner-level students with…

  3. Computational Chemistry Data Management Platform Based on the Semantic Web.

    PubMed

    Wang, Bing; Dobosh, Paul A; Chalk, Stuart; Sopek, Mirek; Ostlund, Neil S

    2017-01-12

    This paper presents a formal data publishing platform for computational chemistry using semantic web technologies. This platform encapsulates computational chemistry data from a variety of packages in an Extensible Markup Language (XML) file called CSX (Common Standard for eXchange). On the basis of a Gainesville Core (GC) ontology for computational chemistry, a CSX XML file is converted into the JavaScript Object Notation for Linked Data (JSON-LD) format using an XML Stylesheet Language Transformation (XSLT) file. Ultimately the JSON-LD file is converted to subject-predicate-object triples in a Turtle (TTL) file and published on the web portal. By leveraging semantic web technologies, we are able to place computational chemistry data onto web portals as a component of a Giant Global Graph (GGG) such that computer agents, as well as individual chemists, can access the data.

  4. Interface Immobilization Chemistry of cRGD-based Peptides Regulates Integrin Mediated Cell Adhesion

    PubMed Central

    Pallarola, Diego; Bochen, Alexander; Boehm, Heike; Rechenmacher, Florian; Sobahi, Tariq R; Spatz, Joachim P; Kessler, Horst

    2014-01-01

    The interaction of specific surface receptors of the integrin family with different extracellular matrix-based ligands is of utmost importance for the cellular adhesion process. A ligand consists of an integrin-binding group, here cyclic RGDfX, a spacer molecule that lifts the integrin-binding group from the surface and a surface anchoring group. c(-RGDfX-) peptides are bound to gold nanoparticle structured surfaces via polyproline, polyethylene glycol or aminohexanoic acid containing spacers of different lengths. Although keeping the integrin-binding c(-RGDfX-) peptides constant for all compounds, changes of the ligand's spacer chemistry and length reveal significant differences in cell adhesion activation and focal adhesion formation. Polyproline-based peptides demonstrate improved cell adhesion kinetics and focal adhesion formation compared with common aminohexanoic acid or polyethylene glycol spacers. Binding activity can additionally be improved by applying ligands with two head groups, inducing a multimeric effect. This study gives insights into spacer-based differences in integrin-driven cell adhesion processes and remarkably highlights the polyproline-based spacers as suitable ligand-presenting templates for surface functionalization. PMID:25810710

  5. Wet-chemistry based selective coatings for concentrating solar power

    NASA Astrophysics Data System (ADS)

    Maimon, Eran; Kribus, Abraham; Flitsanov, Yuri; Shkolnik, Oleg; Feuermann, Daniel; Zwicker, Camille; Larush, Liraz; Mandler, Daniel; Magdassi, Shlomo

    2013-09-01

    Spectrally selective coatings are common in low and medium temperature solar applications from solar water heating collectors to parabolic trough absorber tubes. They are also an essential element for high efficiency in higher temperature Concentrating Solar Power (CSP) systems. Selective coatings for CSP are usually prepared using advanced expensive methods such as sputtering and vapor deposition. In this work, coatings were prepared using low-cost wet-chemistry methods. Solutions based on Alumina and Silica sol gel were prepared and then dispersed with black spinel pigments. The black dispersions were applied by spray/roll coating methods on stainless steel plates. The spectral emissivity of sample coatings was measured in the temperature range between 200 and 500°C, while the spectral absorptivity was measured at room temperature and 500°C. Emissivity at wavelengths of 0.4-1.7 μm was evaluated indirectly using multiple measurements of directional reflectivity. Emissivity at wavelengths 2-14 μm was measured directly using a broadband IR camera that acquires the radiation emitted from the sample, and a range of spectral filters. Emissivity measurement results for a range of coated samples will be presented, and the impact of coating thickness, pigment loading, and surface preparation will be discussed.

  6. Quantum-chemistry descriptors for photosensitizers based on macrocycles.

    PubMed

    Bettanin, Fernanda; Antonio, Felipe C T; Honorio, Kathia M; Homem-de-Mello, Paula

    2017-02-01

    Phthalocyanines, porphyrins, and chlorins have been widely studied as photosensitizers. Both experimental and computational strategies are employed in order to propose new and more active molecules derived from those macrocycles. In this context, there are two main strategies used: (i) the addition of different substituents and (ii) the complexation of the macrocycle with different metallic ions. In this work, we present selected descriptors based on quantum chemistry calculations for forty macrocycles, including some approved drugs. We have found that density functional theory is a suitable methodology to study the large sets of molecules when applying the B3LYP/LanL2DZ methodology for geometry optimization and TD-OLYP/6-31G(d) for absorption spectrum. The inclusion of solvent effects by means of continuum model is important in order to obtain the accurate electronic data. We have verified that by bonding charged or polar substituents to the macrocycle, it is possible to enhance water solvation as well as to improve spectroscopic properties because molecular orbital contributions for Q band can be affected by some substituents. Selected descriptors, electronic and steric, were pointed out as important to propose the new photosensitizers.

  7. SRAT CHEMISTRY AND ACID CONSUMPTION DURING SIMULATED DWPF MELTER FEED PREPARATION

    SciTech Connect

    Koopman, D; David Best, D; Bradley Pickenheim, B

    2008-12-03

    Due to higher than expected hydrogen generation during the Tank 51-Sludge Batch 4 (SB4) qualification run, DWPF engineering requested the Savannah River National Laboratory (SRNL) to expand the ongoing catalytic hydrogen generation program. The work presented in this Technical Report was identified as part of SRNL/Liquid Waste Organization (LWO) meetings to define potential causes of catalytic hydrogen generation as well as from an external technical review panel commissioned to evaluate SRNL hydrogen related data and programs. New scope included improving the understanding of SRAT/SME process chemistry, particularly as it related to acid consumption and hydrogen generation. The expanded hydrogen program scope was covered under the technical task request (TTR): HLW-DWPF-TTR-2007-0016. A task technical and quality assurance plan (TT&QAP) was issued to cover focus areas raised in meetings with LWO plus a portion of the recommendations made by the review panel. A supporting analytical study plan was issued. It was also noted in the review of catalytic hydrogen generation that control of the DWPF acid stoichiometry was an important element in controlling hydrogen generation. A separate TTR was issued to investigate ways of improving the determination of the acid requirement during processing: HLWDWPF-TTR-0015. A separate TT&QAP was prepared for this task request. This report discusses some progress on this task related to developing alternative acid equations and to performing experimental work to supplement the existing database. Simulant preparation and preliminary flowsheet studies were already documented. The prior work produced a sufficient quantity of simulant for the hydrogen program and melter feed rheology testing. It also defined a suitable acid addition stoichiometry. The results presented in this report come from samples and process data obtained during sixteen 22-L SRAT/SME simulations that were performed in the second half of 2007 to produce eight SME

  8. Mechanistic Insights on the Photosensitized Chemistry of a Fatty Acid at the Air/Water Interface

    PubMed Central

    2016-01-01

    Interfaces are ubiquitous in the environment and many atmospheric key processes, such as gas deposition, aerosol, and cloud formation are, at one stage or another, strongly impacted by physical and chemical processes occurring at interfaces. Here, the photoinduced chemistry of an air/water interface coated with nonanoic acid—a fatty acid surfactant we use as a proxy for chemically complex natural aqueous surface microlayers—was investigated as a source of volatile and semivolatile reactive organic species. The carboxylic acid coating significantly increased the propensity of photosensitizers, chosen to mimic those observed in real environmental waters, to partition to the interface and enhance reactivity there. Photochemical formation of functionalized and unsaturated compounds was systematically observed upon irradiation of these coated surfaces. The role of a coated interface appears to be critical in providing a concentrated medium allowing radical–radical reactions to occur in parallel with molecular oxygen additions. Mechanistic insights are provided from extensive analysis of products observed in both gas and aqueous phases by online switchable reagent ion-time of flight-mass spectrometry and by off-line ultraperformance liquid chromatography coupled to a Q Exactive high resolution mass spectrometer through heated electrospray ionization, respectively. PMID:27611489

  9. An Investigation into the Effectiveness of Problem-Based Learning in a Physical Chemistry Laboratory Course

    ERIC Educational Resources Information Center

    Gurses, Ahmet; Acikyildiz, Metin; Dogar, Cetin; Sozbilir, Mustafa

    2007-01-01

    The aim of this study was to investigate the effectiveness of a problem-based learning (PBL) approach in a physical chemistry laboratory course. The parameters investigated were students' attitudes towards a chemistry laboratory course, scientific process skills of students and their academic achievement. The design of the study was one group…

  10. Life-Cycle Analysis and Inquiry-Based Learning in Chemistry Teaching

    ERIC Educational Resources Information Center

    Juntunen, Marianne; Aksela, Maija

    2013-01-01

    The purpose of this design research is to improve the quality of environmental literacy and sustainability education in chemistry teaching through combining a socio-scientific issue, life-cycle analysis (LCA), with inquiry-based learning (IBL). This first phase of the cyclic design research involved 20 inservice trained chemistry teachers from…

  11. Effects of Computer Based Learning on Students' Attitudes and Achievements towards Analytical Chemistry

    ERIC Educational Resources Information Center

    Akcay, Hüsamettin; Durmaz, Asli; Tüysüz, Cengiz; Feyzioglu, Burak

    2006-01-01

    The aim of this study was to compare the effects of computer-based learning and traditional method on students' attitudes and achievement towards analytical chemistry. Students from Chemistry Education Department at Dokuz Eylul University (D.E.U) were selected randomly and divided into three groups; two experimental (Eg-1 and Eg-2) and a control…

  12. Is Case-Based Instruction Effective in Enhancing High School Students' Motivation toward Chemistry?

    ERIC Educational Resources Information Center

    Yalcinkaya, Eylem; Boz, Yezdan; Erdur-Baker, Ozgur

    2012-01-01

    The aim of this study was to investigate the effectiveness of case-based learning (CBL) over traditionally designed chemistry instruction (TDCI) on 10th grade students' perceived motivation about chemistry as a school subject. Two classes were randomly selected from a high school. One class was assigned to be an experimental group and the other…

  13. Stimulating Students' Intrinsic Motivation for Learning Chemistry through the Use of Context-Based Learning Modules

    ERIC Educational Resources Information Center

    Vaino, Katrin; Holbrook, Jack; Rannikmae, Miia

    2012-01-01

    This paper introduces a research project in which five chemistry teachers, working in cooperation with university researchers, implemented a new teaching approach using context-based modules specially designed to stimulate the intrinsic motivation of students. The intention was to induce change in chemistry teachers' teaching approach from more…

  14. Using Structure-Based Organic Chemistry Online Tutorials with Automated Correction for Student Practice and Review

    ERIC Educational Resources Information Center

    O'Sullivan, Timothy P.; Hargaden, Gra´inne C.

    2014-01-01

    This article describes the development and implementation of an open-access organic chemistry question bank for online tutorials and assessments at University College Cork and Dublin Institute of Technology. SOCOT (structure-based organic chemistry online tutorials) may be used to supplement traditional small-group tutorials, thereby allowing…

  15. A Tiny Adventure: The Introduction of Problem Based Learning in an Undergraduate Chemistry Course

    ERIC Educational Resources Information Center

    Williams, Dylan P.; Woodward, Jonathan R.; Symons, Sarah L.; Davies, David L.

    2010-01-01

    Year 1 of the chemistry degree at the University of Leicester has been significantly changed by the integration of a problem based learning (PBL) component into the introductory inorganic/physical chemistry module, "Chemical Principles". Small groups of 5-6 students were given a series of problems with real world scenarios and were then…

  16. What Does the Acid Ionization Constant Tell You? An Organic Chemistry Student Guide

    ERIC Educational Resources Information Center

    Rossi, Robert D.

    2013-01-01

    Many students find the transition from first-year general chemistry to second-year organic chemistry a daunting task. There are many reasons for this, not the least of which is their lack of a solid understanding and appreciation of the importance of some basic concepts and principles from general chemistry that play an extremely critical role in…

  17. Emergence, Learning Difficulties, and Misconceptions in Chemistry Undergraduate Students' Conceptualizations of Acid Strength

    ERIC Educational Resources Information Center

    Tümay, Halil

    2016-01-01

    Philosophical debates about chemistry have clarified that the issue of emergence plays a critical role in the epistemology and ontology of chemistry. In this article, it is argued that the issue of emergence has also significant implications for understanding learning difficulties and finding ways of addressing them in chemistry. Particularly, it…

  18. Palm-Based Data Acquisition Solutions for the Undergraduate Chemistry Laboratory

    NASA Astrophysics Data System (ADS)

    Hudgins, Susan; Qin, Yu; Bakker, Eric; Shannon, Curtis

    2003-11-01

    Handheld computers provide a compact and cost-effective means to log data in the undergraduate chemistry laboratory. Handheld computers have the ability to record multiple forms of data, be programmed for specific projects, and later have data transferred to a personal computer for manipulation and analysis. They are more affordable than notebook computers and are more widely applicable than programmable calculators. This study focuses on acid base titration experiments that are commonly used in introductory chemistry courses. We wrote an interactive Basic language program that allowed a Palm device to measure pH during the course of a titration, and we used a compatible interface for the data acquisition, which we found to record accurate voltage measurements. After synchronizing the device to a laboratory workstation, the experimental data could be transferred into a spreadsheet file, viewed in graphical form and analyzed. Many other applications of handheld computers in the laboratory are possible with the ability to write individual programs on a handheld device. Therefore, the Palm's size, ease of use, and affordability make it an attractive alternative to previous data acquisition methods for use in the chemical laboratory.

  19. Watershed surveys to support an assessment of the regional effects of acidic deposition on surface water chemistry

    NASA Astrophysics Data System (ADS)

    Lee, Jeffrey; Church, Robbins; Lammers, Duane; Liegel, Leon; Johnson, Mark; Coffey, Deborah; Holdren, Richard; Stevens, Donald; Turner, Robert; Blume, Louis

    1989-01-01

    Through the Direct/Delayed Response Project (DDRP), the United States Environmental Protection Agency is attempting to assess the risk to surface waters from acidic deposition in three regions of the eastern United States: the Northeast Region, the Southern Blue Ridge Province, and the Mid-Appalachian Region. The central policy question being addressed by the DDRP is: Within the regions of concern, how many surface water systems (lakes, streams) will become acidic due to current or altered levels of acidic sulfur deposition, and on what time scales? The approach taken by the DDRP is to select a statistically representative set of watersheds in each region of concern and to project the future response of each watershed to various assumed levels of acidic deposition. The probability structure will then be used to extrapolate the watershed-specific results to each region. The data will be used also for statistical investigation of hypothesized relationships between current surface water chemistry and watershed characteristics. Because the needed terrestrial data base was not available, regional watershed surveys were conducted to meet the specific data needs of the DDRP. Maps (1∶24,000) of soils, vegetation, land use, depth to bedrock, and bedrock geology were made for each watershed. The soils were grouped into sampling classes based on their hypothesized response to acidic deposition. Randomized sampling of these classes provided regional means and variances of soil properties that can be applied to individual watersheds. Because of DDRP's need for consistency within and among regions, unique quality control/quality assurance activities were developed and implemented. After verification and validation, the DDRP data base will be made publicly available. This will be a unique and useful resource for others investigating watershed relationships on a regional scale. The results of these surveys and the conclusions of the DDRP will be presented in several future

  20. State of the art of Lewis acid-containing zeolites: lessons from fine chemistry to new biomass transformation processes.

    PubMed

    Moliner, Manuel

    2014-03-21

    The former synthesis of TS-1 opened new catalytic opportunities for zeolites, especially for their application as selective redox catalysts in several fine chemistry processes. Interestingly, isolated Ti species in the framework positions of hydrophobic zeolites, such as high silica zeolites, offer unique Lewis acid sites even in the presence of protic polar solvents (such as water). Following this discovery, other transition metals (such as Sn, Zr, V, Nb, among others) have been introduced in the framework positions of different hydrophobic zeolitic structures, allowing their application in new fine chemistry processes as very active and selective redox catalysts. Recently, these hydrophobic metallozeolites have been successfully applied as efficient catalysts for several biomass-transformation processes in bulk water. The acquired knowledge from the former catalytic descriptions in fine chemistry processes using hydrophobic Lewis acid-containing zeolites has been essential for their application in these novel biomass transformations. In the present review, I will describe the recent advances in the synthesis of new transition metal-containing zeolites presenting Lewis acid character, and their unique catalytic applications in both fine chemistry and novel biomass-transformations.

  1. Study to evaluate the integration of a mass spectrometer with a wet chemistry instrument. [for amino acid analysis

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The charactertistics and performance capability of the current Viking '75 Gas Chromatograph/Mass Spectrometer Instrument are reviewed and documented for the purpose of possible integration with a wet chemistry instrument. Interface, high mass discrimination, and vacuum requirements were determined in a simulated flight investigation. Suggestions for future investigations, tradeoff studies, and design modifications are presented, along with the results of column bleed measurements. A preliminary design of an integrated Wet Chemistry/Mass Spectrometer instrument for amino acid analysis is shown, including estimates of additional weight, volume, and power requirements.

  2. Design of stereoelectronically promoted super lewis acids and unprecedented chemistry of their complexes.

    PubMed

    Foroutan-Nejad, Cina; Vicha, Jan; Marek, Radek

    2014-09-01

    A new family of stereoelectronically promoted aluminum and scandium super Lewis acids is introduced on the basis of state-of-the-art computations. Structures of these molecules are designed to minimize resonance electron donation to central metal atoms in the Lewis acids. Acidity of these species is evaluated on the basis of their fluoride-ion affinities relative to the antimony pentafluoride reference system. It is demonstrated that introduced changes in the stereochemistry of the designed ligands increase acidity considerably relative to Al and Sc complexes with analogous monodentate ligands. The high stability of fluoride complexes of these species makes them ideal candidates to be used as weakly coordinating anions in combination with highly reactive cations instead of conventional Lewis acid-fluoride complexes. Further, the interaction of all designed molecules with methane is investigated. All studied acids form stable pentavalent-carbon complexes with methane. In addition, interactions of the strongest acid of this family with very weak bases, namely, H2, N2, carbon oxides, and noble gases were investigated; it is demonstrated that this compound can form considerably stable complexes with the aforementioned molecules. To the best of our knowledge, carbonyl and nitrogen complexes of this species are the first hypothetical four-coordinated carbonyl and nitrogen complexes of aluminum. The nature of bonding in these systems is studied in detail by various bonding analysis approaches.

  3. Characterizing Surface Acidic Sites in Mesoporous-Silica-Supported Tungsten Oxide Catalysts Using Solid State NMR and Quantum Chemistry Calculations

    SciTech Connect

    Hu, Jian Z.; Kwak, Ja Hun; Wang, Yong; Hu, Mary Y.; Turcu, Romulus VF; Peden, Charles HF

    2011-10-18

    The acidic sites in dispersed tungsten oxide supported on SBA-15 mesoporous silica were investigated using a combination of pyridine titration, both fast-, and slow-MAS {sup 15}N NMR, static {sup 2}H NMR, and quantum chemistry calculations. It is found that the bridged acidic -OH groups in surface adsorbed tungsten dimers (i.e., W-OH-W) are the Broensted acid sites. The unusually strong acidity of these Broensted acid sites is confirmed by quantum chemistry calculations. In contrast, terminal W-OH sites are very stable and only weakly acidic as are terminal Si-OH sites. Furthermore, molecular interactions between pyridine molecules and the dimer Broensted and terminal W-OH sites for dispersed tungsten oxide species is strong. This results in restricted molecular motion for the interacting pyridine molecules even at room temperature, i.e., a reorientation mainly about the molecular 2-fold axis. This restricted reorientation makes it possible to estimate the relative ratio of the Broensted (tungsten dimer) to the weakly acidic terminal W-OH sites in the catalyst using the slow-MAS {sup 1}H-{sup 15}N CP PASS method.

  4. On-Line Data Bases in Chemistry Literature Education.

    ERIC Educational Resources Information Center

    Drum, Carol A.; Pope, Nolan F.

    1979-01-01

    Describes a program developed to expose college chemistry students to some of the more modern information retrieval tools, as computerized online databases. Following classroom lectures and discussions, students individually develop a search statement relevant to their own research needs and run it in the Chemical Abstracts files. (BT)

  5. Design, Development, and Psychometric Analysis of a General, Organic, and Biological Chemistry Topic Inventory Based on the Identified Main Chemistry Topics Relevant to Nursing Clinical Practice

    ERIC Educational Resources Information Center

    Brown, Corina E.

    2013-01-01

    This two-stage study focused on the undergraduate nursing course that covers topics in general, organic, and biological (GOB) chemistry. In the first stage, the central objective was to identify the main concepts of GOB chemistry relevant to the clinical practice of nursing. The collection of data was based on open-ended interviews of both nursing…

  6. The EPA Comptox Chemistry Dashboard: A Web-Based Data Integration Hub for Toxicology Data (SOT)

    EPA Science Inventory

    The U.S. Environmental Protection Agency (EPA) Computational Toxicology Program integrates advances in biology, chemistry, and computer science to help prioritize chemicals for further research based on potential human health risks. This work involves computational and data drive...

  7. Integration of Environmental Analytical Chemistry with Environmental Law: The Development of a Problem-Based Laboratory.

    ERIC Educational Resources Information Center

    Cancilla, Devon A.

    2001-01-01

    Introduces an undergraduate level problem-based analytical chemistry laboratory course integrated with an environmental law course. Aims to develop an understanding among students on the use of environmental indicators for environmental evaluation. (Contains 30 references.) (YDS)

  8. Nucleic acid chemistry in the organic phase: from functionalized oligonucleotides to DNA side chain polymers.

    PubMed

    Liu, Kai; Zheng, Lifei; Liu, Qing; de Vries, Jan Willem; Gerasimov, Jennifer Y; Herrmann, Andreas

    2014-10-08

    DNA-incorporating hydrophobic moieties can be synthesized by either solid-phase or solution-phase coupling. On a solid support the DNA is protected, and hydrophobic units are usually attached employing phosphoramidite chemistry involving a DNA synthesizer. On the other hand, solution coupling in aqueous medium results in low yields due to the solvent incompatibility of DNA and hydrophobic compounds. Hence, the development of a general coupling method for producing amphiphilic DNA conjugates with high yield in solution remains a major challenge. Here, we report an organic-phase coupling strategy for nucleic acid modification and polymerization by introducing a hydrophobic DNA-surfactant complex as a reactive scaffold. A remarkable range of amphiphile-DNA structures (DNA-pyrene, DNA-triphenylphosphine, DNA-hydrocarbon, and DNA block copolymers) and a series of new brush-type DNA side-chain homopolymers with high DNA grafting density are produced efficiently. We believe that this method is an important breakthrough in developing a generalized approach to synthesizing functional DNA molecules for self-assembly and related technological applications.

  9. On the cellular metabolism of the click chemistry probe 19-alkyne arachidonic acid.

    PubMed

    Robichaud, Philippe Pierre; Poirier, Samuel J; Boudreau, Luc H; Doiron, Jérémie A; Barnett, David A; Boilard, Eric; Surette, Marc E

    2016-10-01

    Alkyne and azide analogs of natural compounds that can be coupled to sensitive tags by click chemistry are powerful tools to study biological processes. Arachidonic acid (AA) is a FA precursor to biologically active compounds. 19-Alkyne-AA (AA-alk) is a sensitive clickable AA analog; however, its use as a surrogate to study AA metabolism requires further evaluation. In this study, AA-alk metabolism was compared with that of AA in human cells. Jurkat cell uptake of AA was 2-fold greater than that of AA-alk, but significantly more AA-Alk was elongated to 22:4. AA and AA-alk incorporation into and remodeling between phospholipid (PL) classes was identical indicating equivalent CoA-independent AA-PL remodeling. Platelets stimulated in the pre-sence of AA-alk synthesized significantly less 12-lipoxygenase (12-LOX) and cyclooxygenase products than in the presence of AA. Ionophore-stimulated neutrophils produced significantly more 5-LOX products in the presence of AA-alk than AA. Neutrophils stimulated with only exogenous AA-alk produced significantly less 5-LOX products compared with AA, and leukotriene B4 (LTB4)-alk was 12-fold less potent at stimulating neutrophil migration than LTB4, collectively indicative of weaker leukotriene B4 receptor 1 agonist activity of LTB4-alk. Overall, these results suggest that the use of AA-alk as a surrogate for the study of AA metabolism should be carried out with caution.

  10. Effect of Organic Coatings, Humidity and Aerosol Acidity on Multiphase Chemistry of Isoprene Epoxydiols

    SciTech Connect

    Riva, Matthieu; Bell, David M.; Hansen, Anne-Maria Kaldal; Drozd, Greg T.; Zhang, Zhenfa; Gold, Avram; Imre, Dan; Surratt, Jason D.; Glasius, Marianne; Zelenyuk, Alla

    2016-06-07

    Multiphase chemistry of isomeric isoprene epoxydiols (IEPOX) has been shown to be the dominant source of isoprene-derived secondary organic aerosol (SOA). Recent studies have reported particles composed of ammonium bisulfate (ABS) mixed with model organics exhibit slower rates of IEPOX uptake. In the present study, we investigate the effect of atmospherically-relevant organic coatings of α-pinene (AP) SOA on the reactive uptake of trans-β-IEPOX onto ABS particles under different conditions and coating thicknesses. Single particle mass spectrometry was used to characterize in real-time particle size, shape, density, and quantitative composition before and after reaction with IEPOX. We find that IEPOX uptake by pure sulfate particles is a volume-controlled process, which results in particles with uniform concentration of IEPOX-derived SOA across a wide range of sizes. Aerosol acidity was shown to enhance IEPOX-derived SOA formation, consistent with recent studies. The presence of water has a weaker impact on IEPOX-derived SOA yield, but significantly enhanced formation of 2-methyltetrols, consistent with offline filter analysis. In contrast, IEPOX uptake by ABS particles coated by AP-derived SOA is strongly dependent on particle size and composition. IEPOX uptake occurred only when weight fraction of AP-derived SOA dropped below 50 %, effectively limiting IEPOX uptake to larger particles.

  11. The effects of borate minerals on the synthesis of nucleic acid bases, amino acids and biogenic carboxylic acids from formamide.

    PubMed

    Saladino, Raffaele; Barontini, Maurizio; Cossetti, Cristina; Di Mauro, Ernesto; Crestini, Claudia

    2011-08-01

    The thermal condensation of formamide in the presence of mineral borates is reported. The products afforded are precursors of nucleic acids, amino acids derivatives and carboxylic acids. The efficiency and the selectivity of the reaction was studied in relation to the elemental composition of the 18 minerals analyzed. The possibility of synthesizing at the same time building blocks of both genetic and metabolic apparatuses, along with the production of amino acids, highlights the interest of the formamide/borate system in prebiotic chemistry.

  12. Students' Perceptions of Teaching in Context-Based and Traditional Chemistry Classrooms: Comparing Content, Learning Activities, and Interpersonal Perspectives

    ERIC Educational Resources Information Center

    Overman, Michelle; Vermunt, Jan D.; Meijer, Paulien C.; Bulte, Astrid M. W.; Brekelmans, Mieke

    2014-01-01

    Context-based curriculum reforms in chemistry education are thought to bring greater diversity to the ways in which chemistry teachers organize their teaching. First and foremost, students are expected to perceive this diversity. However, empirical research on how students perceive their teacher's teaching in context-based chemistry classrooms,…

  13. Teachers' Perceptions of the Teaching of Acids and Bases in Swedish Upper Secondary Schools

    ERIC Educational Resources Information Center

    Drechsler, Michal; Van Driel, Jan

    2009-01-01

    We report in this paper on a study of chemistry teachers' perceptions of their teaching in upper secondary schools in Sweden, regarding models of acids and bases, especially the Bronsted and the Arrhenius model. A questionnaire consisting of a Likert-type scale was developed, which focused on teachers' knowledge of different models, knowledge of…

  14. Filtrates & Residues. Acid Pickling with Amines: An Experiment in Applied Chemistry for High School or Freshman Chemistry.

    ERIC Educational Resources Information Center

    Spears, Steven G.; And Others

    1988-01-01

    This article gives a brief description of the process of the removal of corrosion and millscale from the surfaces of ferrous metals by acid pickling. It suggests an experiment to illustrate this process including the procedure and a discussion of the results. (CW)

  15. 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.

  16. 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.

  17. Students' Perceptions of Teaching in Context-based and Traditional Chemistry Classrooms: Comparing content, learning activities, and interpersonal perspectives

    NASA Astrophysics Data System (ADS)

    Overman, Michelle; Vermunt, Jan D.; Meijer, Paulien C.; Bulte, Astrid M. W.; Brekelmans, Mieke

    2014-07-01

    Context-based curriculum reforms in chemistry education are thought to bring greater diversity to the ways in which chemistry teachers organize their teaching. First and foremost, students are expected to perceive this diversity. However, empirical research on how students perceive their teacher's teaching in context-based chemistry classrooms, and whether this teaching differs from traditional chemistry lessons, is scarce. This study aims to develop our understanding of what teaching looks like, according to students, in context-based chemistry classrooms compared with traditional chemistry classrooms. As such, it might also provide a better understanding of whether teachers implement and attain the intentions of curriculum developers. To study teacher behaviour we used three theoretical perspectives deemed to be important for student learning: a content perspective, a learning activities perspective, and an interpersonal perspective. Data were collected from 480 students in 24 secondary chemistry classes in the Netherlands. Our findings suggest that, according to the students, the changes in teaching in context-based chemistry classrooms imply a lessening of the emphasis on fundamental chemistry and the use of a teacher-centred approach, compared with traditional chemistry classrooms. However, teachers in context-based chemistry classrooms seem not to display more 'context-based' teaching behaviour, such as emphasizing the relation between chemistry, technology, and society and using a student-centred approach. Furthermore, students in context-based chemistry classrooms perceive their teachers as having less interpersonal control and showing less affiliation than teachers in traditional chemistry classrooms. Our findings should be interpreted in the context of former and daily experiences of both teachers and students. As only chemistry is reformed in the schools in which context-based chemistry is implemented, it is challenging for both students and teachers to

  18. White biotechnology for green chemistry: fermentative 2-oxocarboxylic acids as novel building blocks for subsequent chemical syntheses.

    PubMed

    Stottmeister, U; Aurich, A; Wilde, H; Andersch, J; Schmidt, S; Sicker, D

    2005-12-01

    Functionalized compounds, which are difficult to produce by classical chemical synthesis, are of special interest as biotechnologically available targets. They represent useful building blocks for subsequent organic syntheses, wherein they can undergo stereoselective or regioselective reactions. "White Biotechnology" (as defined by the European Chemical Industry [ http://www.europabio.org/white_biotech.htm ], as part of a sustainable "Green Chemistry,") supports new applications of chemicals produced via biotechnology. Environmental aspects of this interdisciplinary combination include: Use of renewable feedstock Optimization of biotechnological processes by means of: New "high performance" microorganisms On-line measurement of substrates and products in bioreactors Alternative product isolation, resulting in higher yields, and lower energy demand In this overview we describe biotechnologically produced pyruvic, 2-oxopentaric and 2-oxohexaric acids as promising new building blocks for synthetic chemistry. In the first part, the microbial formation of 2-oxocarboxylic acids (2-OCAs) in general, and optimization of the fermentation steps required to form pyruvic acid, 2-oxoglutaric acid, and 2-oxo-D-gluconic acid are described, highlighting the fundamental advantages in comparison to chemical syntheses. In the second part, a set of chemical formula schemes demonstrate that 2-OCAs are applicable as building blocks in the chemical synthesis of, e.g., hydrophilic triazines, spiro-connected heterocycles, benzotriazines, and pyranoic amino acids. Finally, some perspectives are discussed.

  19. 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…

  20. 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…

  1. Trends in summer chemistry linked to productivity in lakes recovering from acid deposition in the Adirondack region of New York

    USGS Publications Warehouse

    Momen, B.; Lawrence, G.B.; Nierzwicki-Bauer, S. A.; Sutherland, J.W.; Eichler, L.W.; Harrison, J.P.; Boylen, C.W.

    2006-01-01

    The US Environmental Protection Agency established the Adirondack Effects Assessment Program (AEAP) to evaluate and monitor the status of biological communities in lakes in the Adirondack region of New York that have been adversely affected by acid deposition. This program includes chemical analysis of 30 lakes, sampled two to three times each summer. Results of trends analysis for lake chemistry and chlorophyll a (chlor a) are presented for 1994 to 2003, and a general comparison is made with recent results of the Adirondack Long-Term Monitoring (ALTM) Program, which included chemical analysis of all but two of these lakes (plus an additional 24 lakes) monthly, year-round for 1992-2004. Increases in pH were found in 25 of the 30 AEAP lakes (P < 0.05) and increases in acid-neutralizing capacity (ANC) were found in 12 of the 30 lakes (P < 0.05). Concentrations of both SO 42- and Mg 2+ decreased in 11 lakes (P < 0.05), whereas concentrations of NO 3- decreased in 20 lakes (P < 0.05). Concentrations of NH 4+ decreased in 10 lakes at a significance level of P < 0.05 and in three other lakes based on P < 0.1. Concentrations of inorganic and organic monomeric aluminum generally were below the reporting limit of 1.5 ??mol L-1, but decreases were detected in four and five lakes, respectively (P < 0.1). Concentrations of chlor a increased in seven lakes at a significance level of P < 0.05 and two lakes at a significance level of P < 0.1. A significant inverse correlation was also found between chlor a and NO 3- concentrations in nine lakes at a significance level of P < 0.05 and two lakes at a significance level of P < 0.1. Results of AEAP analysis of lake chemistry were similar to those of the ALTM Program, although decreases in SO 42- concentrations were more evident in the year-round ALTM record. Overall, the results suggest (a) a degree of chemical recovery from acidification during the summer, (b) an increase in phytoplankton productivity, and (c) a decreasing trend in

  2. Stratospheric Sulfuric Acid and Black Carbon Aerosol Measured During POLARIS and its Role in Ozone Chemistry

    NASA Technical Reports Server (NTRS)

    Strawa, Anthony W.; Pueschel, R. F.; Drdla, K.; Verma, S.; Gore, Warren J. (Technical Monitor)

    1998-01-01

    Stratospheric aerosol can affect the environment in three ways. Sulfuric acid aerosol have been shown to act as sites for the reduction of reactive nitrogen and chlorine and as condensation sites to form Polar Stratospheric Clouds, under very cold conditions, which facilitate ozone depletion. Recently, modeling studies have suggested a link between BCA (Black Carbon Aerosol) and ozone chemistry. These studies suggest that HNO3, NO2, and O3 may be reduced heterogeneously on BCA particles. The ozone reaction converts ozone to oxygen molecules, while HNO3 and NO2 react to form NOx. Finally, a buildup of BCA could reduce the single-scatter albedo of aerosol below a value of 0.98, a critical value that has been postulated to change the effect of stratospheric aerosol from cooling to warming. Correlations between measured BCA amounts and aircraft usage have been reported. Attempts to link BCA to ozone chemistry and other stratospheric processes have been hindered by questions concerning the amount of BCA that exists in the stratosphere, the magnitude of reaction probabilities, and the scarcity of BCA measurements. The Ames Wire Impactors (AWI) participated in POLARIS as part of the complement of experiments on the NASA ER-2. One of our main objectives was to determine the amount of aerosol surface area, particularly BCA, available for reaction with stratospheric constituents and assess if possible, the importance of these reactions. The AWI collects aerosol and BCA particles on thin Palladium wires that are exposed to the ambient air in a controlled manner. The samples are returned to the laboratory for subsequent analysis. The product of the AWI analysis is the size, surface area, and volume distributions, morphology and elemental composition of aerosol and BCA. This paper presents results from our experiments during POLARIS and puts these measurements in the context of POLARIS and other missions in which we have participated. It describes modifications to the AWI data

  3. Medicinal Chemistry Projects Requiring Imaginative Structure-Based Drug Design Methods.

    PubMed

    Moitessier, Nicolas; Pottel, Joshua; Therrien, Eric; Englebienne, Pablo; Liu, Zhaomin; Tomberg, Anna; Corbeil, Christopher R

    2016-09-20

    cytochrome P450 enzymes (CYPs)-for toxicology studies-the program Impacts was derived from Fitted and helped us to reveal a complex metabolism with unforeseen stereocenter isomerizations. These efforts, combined with those of other docking software developers, have strengthened our understanding of the complex drug-protein binding process while providing the medicinal chemistry community with useful tools that have led to drug discoveries. In this Account, we describe our contributions over the past 15 years-within their historical context-to the design of drug candidates, including BACE-1 inhibitors, POP covalent inhibitors, G-quadruplex binders, and aminoglycosides binding to nucleic acids. We also remark the necessary developments of docking programs, specifically Fitted, that enabled structure-based design to flourish and yielded multiple fruitful, rational medicinal chemistry campaigns.

  4. Key discoveries in bile acid chemistry and biology and their clinical applications: history of the last eight decades

    PubMed Central

    Hofmann, Alan F.; Hagey, Lee R.

    2014-01-01

    During the last 80 years there have been extraordinary advances in our knowledge of the chemistry and biology of bile acids. We present here a brief history of the major achievements as we perceive them. Bernal, a physicist, determined the X-ray structure of cholesterol crystals, and his data together with the vast chemical studies of Wieland and Windaus enabled the correct structure of the steroid nucleus to be deduced. Today, C24 and C27 bile acids together with C27 bile alcohols constitute most of the bile acid “family”. Patterns of bile acid hydroxylation and conjugation are summarized. Bile acid measurement encompasses the techniques of GC, HPLC, and MS, as well as enzymatic, bioluminescent, and competitive binding methods. The enterohepatic circulation of bile acids results from vectorial transport of bile acids by the ileal enterocyte and hepatocyte; the key transporters have been cloned. Bile acids are amphipathic, self-associate in solution, and form mixed micelles with polar lipids, phosphatidylcholine in bile, and fatty acids in intestinal content during triglyceride digestion. The rise and decline of dissolution of cholesterol gallstones by the ingestion of 3,7-dihydroxy bile acids is chronicled. Scientists from throughout the world have contributed to these achievements. PMID:24838141

  5. Response of surface water chemistry to reduced levels of acid precipitation: Comparison of trends in two regions of New York, USA

    USGS Publications Warehouse

    Burns, Douglas A.; McHale, M.R.; Driscoll, C.T.; Roy, K.M.

    2006-01-01

    In light of recent reductions in sulphur (S) and nitrogen (N) emissions mandated by Title IV of the Clean Air Act Amendments of 1990, temporal trends and trend coherence in precipitation (1984-2001 and 1992-2001) and surface water chemistry (1992-2001) were determined in two of the most acid-sensitive regions of North America, i.e. the Catskill and Adirondack Mountains of New York. Precipitation chemistry data from six sites located near these regions showed decreasing sulphate (SO42-), nitrate (NO3-), and base cation (CB) concentrations and increasing pH during 1984-2001, but few significant trends during 1992-2001. Data from five Catskill streams and 12 Adirondack lakes showed decreasing trends in SO42- concentrations at all sites, and decreasing trends in NO3-, CB, and H+ concentrations and increasing trends in dissolved organic carbon at most sites. In contrast, acid-neutralizing capacity (ANC increased significantly at only about half the Adirondack lakes and in one of the Catskill streams. Flow correction prior to trend analysis did not change any trend directions and had little effect on SO42- trends, but it caused several significant non-flow-corrected trends in NO3- and ANC to become non-significant, suggesting that trend results for flow-sensitive constituents are affected by flow-related climate variation. SO42- concentrations showed high temporal coherence in precipitation, surface waters, and in precipitation-surface water comparisons, reflecting a strong link between S emissions, precipitation SO42- concentrations, and the processes that affect S cycling within these regions. NO3- and H+ concentrations and ANC generally showed weak coherence, especially in surface waters and in precipitation-surface water comparisons, indicating that variation in local-scale processes driven by factors such as climate are affecting trends in acid-base chemistry in these two regions. Copyright ?? 2005 John Wiley & Sons, Ltd.

  6. Long term (1987-2012) trends in water chemistry of acid sensitive Swedish lakes

    NASA Astrophysics Data System (ADS)

    Futter, Martyn; Valinia, Salar; Fölster, Jens

    2014-05-01

    Acidification of surface waters is a serious concern in Sweden. During the 1970s and 1980s, many surface waters in Sweden were acidified by long-range pollution. Legislated emissions reductions have led to the recovery of many water bodies but today, there are concerns about the possibility of re-acidification. Sweden is committed to a goal of natural acidification only (i.e. no anthropogenic acidification). Here, we present long term (1987-2012) trends in strong acid anion, base cation, organic carbon and alkalinity measurements. Lakes are defined as acidified in Sweden if pH is more than 0.4 units less than a reference (1860) pH estimated using MAGIC, a widely used process-based model of acidification. Using this criteria, many acid sensitive Swedish lakes are still acidified. A changing climate and more intensive forest harvesting may further delay the recovery from acidification. Average measured alkalinity in the 38 lakes presented here was <= 0.02 mekv/l between 2000-2012. Strong acid anion concentrations declined, primarily as a result of declines in sulfate. Chloride is now the dominant anion in many of these lakes. Base cations concentrations have declined less rapidly, leading to an increase in charge balance ANC. This increase in charge balance ANC has not been matched by an increase in measured alkalinity. Total organic carbon concentrations have increased significantly in many of these lakes, to the point where modeled organic acidity is now approximately equal to inorganic acidity. While the results presented here conform to acidification theory, they illustrate the value of long-term monitoring for assessing the effects of pollutant reduction measures, identifying new threats to water quality and corroborating model results. Most importantly, the long-term monitoring results presented here can be an important tool for informing environmental policy.

  7. 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

    2002-12-06

    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.

  8. Pulsed and continuous wave acrylic acid radio frequency plasma deposits: plasma and surface chemistry.

    PubMed

    Voronin, Sergey A; Zelzer, Mischa; Fotea, Catalin; Alexander, Morgan R; Bradley, James W

    2007-04-05

    Plasma polymers have been formed from acrylic acid using a pulsed power source. An on-pulse duration of 100 micros was used with a range of discharge off-times between 0 (continuous wave) and 20,000 micros. X-ray photoelectron spectroscopy (XPS) has been used in combination with trifluoroethanol (TFE) derivatization to quantify the surface concentration of the carboxylic acid functionality in the deposit. Retention of this functionality from the monomer varied from 2% to 65%. When input power was expressed as the time-averaged energy per monomer molecule, E(mean), the deposit chemistry achieved could be described using a single relationship for all deposition conditions. Deposition rates were monitored using a quartz crystal microbalance, which revealed a range from 20 to 200 microg m(-2) s(-1), and these fell as COOH functional retention increased. The flow rate was found to be the major determinant of the deposition rate, rather than being uniquely defined by E(mean), connected to the rate at which fresh monomer enters the system in the monomer deficient regime. The neutral species were collected in a time-averaged manner. As the energy delivered per molecule in the system (E(mean)) decreased, the amount of intact monomer increased, with the average neutral mass approaching 72 amu as E(mean) tends to zero. No neutral oligomeric species were detected. Langmuir probes have been used to determine the temporal evolution of the density and temperature of the electrons in the plasma and the plasma potential adjacent to the depositing film. It has been found that even 500 micros into the afterglow period that ionic densities are still significant, 5-10% of the on-time density, and that ion accelerating sheath potentials fall from 40 V in the on-time to a few volts in the off-time. We have made the first detailed, time- and energy-resolved mass spectrometry measurements in depositing acrylic acid plasma. These have allowed us to identify and quantify the positive ion

  9. Redox and Lewis acid-base activities through an electronegativity-hardness landscape diagram.

    PubMed

    Das, Ranjita; Vigneresse, Jean-Louis; Chattaraj, Pratim Kumar

    2013-11-01

    Chemistry is the science of bond making and bond breaking which requires redistribution of electron density among the reactant partners. Accordingly acid-base and redox reactions form cardinal components in all branches of chemistry, e.g., inorganic, organic, physical or biochemistry. That is the reason it forms an integral part of the undergraduate curriculum all throughout the globe. In an electronegativity (χ)- hardness (η) landscape diagram the diagonal χ = η line separates reducing agents from oxidizing agents as well as Lewis acids from Lewis bases. While electronegativity is related to the degree of electron transfer between two reactants, hardness is related to the resistance to that process. Accordingly the electronegativities of oxidizing agents/Lewis acids are generally greater than the corresponding hardness values and the reverse is true for reducing agents/Lewis bases. Electrophiles and nucleophiles are also expected to follow similar trends.

  10. Detection of Salicylic Acid in Willow Bark: An Addition to a Classic Series of Experiments in the Introductory Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Clay, Matthew D.; McLeod, Eric J.

    2012-01-01

    Salicylic acid and its derivative, acetylsalicylic acid, are often encountered in introductory organic chemistry experiments, and mention is often made that salicylic acid was originally isolated from the bark of the willow tree. This biological connection, however, is typically not further pursued, leaving students with an impression that biology…

  11. Double electrochemical covalent coupling method based on click chemistry and diazonium chemistry for the fabrication of sensitive amperometric immunosensor.

    PubMed

    Qi, Honglan; Li, Min; Zhang, Rui; Dong, Manman; Ling, Chen

    2013-08-20

    A double electrochemical covalent coupling method based on click chemistry and diazonium chemistry for the fabrication of sensitive amperometric immunosensor was developed. As a proof-of-concept, a designed alkyne functionalized human IgG was used as a capture antibody and a HRP-labeled rabbit anti-goat IgG was used as signal antibody for the determination of the anti-human IgG using the sandwich model. The immunosensor was fabricated by electrochemically grafting a phenylazide on the surface of a glassy carbon electrode, and then, by coupling the alkyne functionalized human IgG with the phenylazide group through an electro-click chemistry in the presence of Cu(II). The amperometric measurement for the determination of the anti-human IgG was performed after the fabricated immunosensor was incubated with the target anti-human IgG and then with the HRP-labeled anti-goat IgG at -0.25V in 0.10M PBS (pH 7.0) containing 0.1mM hydroquinone and 2.0mM H2O2. The results showed that the increased current was linear with the logarithm of the concentration of the anti-human IgG in the range from 1.0×10(-10)g mL(-1) to 1.0×10(-8)g mL(-1) with a detection limit of 3×10(-11)g mL(-1). Furthermore, the feasibility of the double electrochemical covalent coupling method proposed in this work for fabricating the amperometric immunosensor array was explored. This work demonstrates that the double electrochemical covalent coupling method is a promising approach for the fabrication of the immunosensor and immunosensor array.

  12. Chemistry Teachers' Perceived Benefits and Challenges of Inquiry-Based Instruction in Inclusive Chemistry Classrooms

    ERIC Educational Resources Information Center

    Mumba, F.; Banda, A.; Chabalengula, V. M.

    2015-01-01

    Studies on inquiry-based instruction in inclusive science teaching have mainly focused on elementary and middle school levels. Little is known about inquiry-based instruction in high school inclusive science classes. Yet, such classes have become the norm in high schools, fulfilling the instructional needs of students with mild disabilities. This…

  13. Materials Chemistry and Performance of Silicone-Based Replicating Compounds.

    SciTech Connect

    Brumbach, Michael T.; Mirabal, Alex James; Kalan, Michael; Trujillo, Ana B; Hale, Kevin

    2014-11-01

    Replicating compounds are used to cast reproductions of surface features on a variety of materials. Replicas allow for quantitative measurements and recordkeeping on parts that may otherwise be difficult to measure or maintain. In this study, the chemistry and replicating capability of several replicating compounds was investigated. Additionally, the residue remaining on material surfaces upon removal of replicas was quantified. Cleaning practices were tested for several different replicating compounds. For all replicating compounds investigated, a thin silicone residue was left by the replica. For some compounds, additional inorganic species could be identified in the residue. Simple solvent cleaning could remove some residue.

  14. Acid and base degraded products of ketorolac.

    PubMed

    Salaris, Margherita; Nieddu, Maria; Rubattu, Nicola; Testa, Cecilia; Luongo, Elvira; Rimoli, Maria Grazia; Boatto, Gianpiero

    2010-06-05

    The stability of ketorolac tromethamine was investigated in acid (0.5M HCl) and alkaline conditions (0.5M NaOH), using the same procedure reported by Devarajan et al. [2]. The acid and base degradation products were identified by liquid chromatography-mass spectrometry (LC-MS).

  15. Tropospheric chemistry of internally mixed sea salt and organic particles: Surprising reactivity of NaCl with weak organic acids

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Moffet, Ryan C.; Gilles, Mary K.; Fast, Jerome D.; Zaveri, Rahul A.; Wang, Bingbing; Nigge, Pascal; Shutthanandan, Janani

    2012-08-01

    Chemical imaging analysis of internally mixed sea salt/organic particles collected onboard the Department of Energy (DOE) G-1 aircraft during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) was performed using electron microscopy and X-ray spectro-microscopy. Substantial chloride depletion in aged sea salt particles was observed, which could not be explained by the known atmospheric reactivity of sea salt with inorganic nitric and sulfuric acids. We present field evidence that chloride components in sea salt particles may effectively react with organic acids releasing HCl gas to the atmosphere, leaving behind particles depleted in chloride and enriched in the corresponding organic salts. While formation of the organic salts products is not thermodynamically favored for bulk aqueous chemistry, these reactions in aerosol are driven by high volatility and evaporation of the HCl product from drying particles. These field observations were corroborated in a set of laboratory experiments where NaCl particles mixed with organic acids were found to be depleted in chloride. Combined together, the results indicate substantial chemical reactivity of sea salt particles with secondary organics that has been largely overlooked in the atmospheric aerosol chemistry. Atmospheric aging, and in particular hydration-dehydration cycles of mixed sea salt/organic particles, may result in formation of organic salts that will modify the acidity, hygroscopic, and optical properties of aged particles.

  16. Tropospheric Chemistry of Internally Mixed Sea Salt and Organic Particles: Surprising Reactivity of NaCl with Weak Organic Acids

    SciTech Connect

    Laskin, Alexander; Moffet, Ryan C.; Gilles, Marry K.; Fast, Jerome D.; Zaveri, Rahul A.; Wang, Bingbing; Nigge, P.; Shutthanandan, Janani I.

    2012-08-03

    Chemical imaging analysis of internally mixed sea salt/organic particles collected on board the Department of Energy (DOE) G-1 aircraft during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) was performed using electron microscopy and X-ray spectro-microscopy techniques. Substantial chloride depletion in aged sea salt particles was observed, which could not be explained by the known atmospheric reactivity of sea salt with inorganic nitric and sulfuric acids. We present field evidence that chloride components in sea salt particles may effectively react with organic acids releasing HCl gas to the atmosphere, leaving behind particles depleted in chloride and enriched in the corresponding organic salts. While formation of the organic salts products is not thermodynamically favored for bulk aqueous chemistry, these reactions in aerosol are driven by high volatility and irreversible evaporation of the HCl product from drying particles. These field observations were corroborated in a set of laboratory experiments where NaCl particles mixed with organic acids were found to be depleted in chloride. Combined together, the results indicate substantial chemical reactivity of sea salt particles with secondary organics that has been largely overlooked in the atmospheric aerosol chemistry. Atmospheric aging, and especially hydration-dehydration cycles of mixed sea salt/organic particles may result in formation of organic salts that will modify acidity, hygroscopic and optical properties of aged particles.

  17. Solid Acid Based Fuel Cells

    DTIC Science & Technology

    2007-11-02

    superprotonic solid acids with elements such as P, As, Si and Ge, which have greater affinities to oxygen , we anticipate that the reduction reaction will be...bulk material consisted of an apatite phase (hexagonal symmetry) of variable composition, LixLa10-x(SiO4)6O3-x, with excess lithium residing in the...in Tables 1 and 2, indicate that this compound is a rather conventional apatite with fixed stoichiometry, LiLa9(SiO4)6O2 (x = 1). Such a result is

  18. Light-induced multiphase chemistry of gas phase ozone on aqueous pyruvic and oxalic acids: Aerosol chamber study

    NASA Astrophysics Data System (ADS)

    Gligorovski, S.; Grgic, I.; Net, S.; Böge, O.; Iinuma, Y.; Kahnt, A.; Scheinhardt, S.; Herrmann, H.; Wortham, H.

    2010-12-01

    The light-absorbing organic compounds present in and on condensed aerosol particles interacting with trace gases such as ozone can initiate a new and potentially important photo-induced multiphase chemistry. However, investigations of light induced multiphase processes are very scarce at present. We have launched the idea of pyruvic acid (PA) acting as a photosensitizer in the multiphase reactions between gas-phase ozone and aqueous oxalic acid (OA). The performed photochemical batch experiments yielded a complex suite of organic molecules which resulted primarily from the oligomerization of OA/PA and subsequent reactions, including decarboxylation and cycloadition (Grgic et al., 2010). In the atmosphere, pyruvic acid will always be accompanied by other carboxylic acids (and also other organics) which are constituents of either aerosol particles or aqueous droplets the effects of a possible photochemistry triggered by pyruvic acid should be experimentally studied in depth and under natural conditions as far as possible. Hence, in a very recent study experiments in the aerosol chamber facility LEAK at IFT, Leipzig, were performed to verify the influence of pyruvic on the multiphase (photo)oxidation of oxalic acid. The aim of these experiments was to study the multiphase photo-induced oxidation reactions with airborne deliquescent particles to demonstrate the applicability of the reactions mentioned above under more realistic conditions than in a batch reactor. State of the art sampling and analytical tools were applied for the analysis of the ongoing chamber runs and the formed particulate products which include denuder sampling, carbonyl compound derivatisation, PTR-MS measurements, GC-MS measurements and HPLC-MS and CE-MS for the particle phase. First results from these joint complex chamber experiments will be presented and discussed. Reference: Grgić I., Nieto-Gligorovski L.I., Net S., Temime-Roussel B., Gligorovski S., Wortham H. Light induced multiphase

  19. Towards Self-Replicating Chemical Systems Based on Cytidylic and Guanylic Acids

    NASA Technical Reports Server (NTRS)

    Kanavarioti, Anastassia

    1999-01-01

    This project was aimed towards a better understanding of template-directed reactions and, based on this, towards the development of efficient non-enzymatic RNA replicating systems. These systems could serve as models for the prebiotic synthesis of an RNA world. The major objectives of this project are: (a) To elucidate the mechanistic aspects of template-directed (TD) chemistry and (b) to identify active boundary regions, or conditions, environmental and other, that favor "organized chemistry" and stereo-selective polymerization of nucleotides. "Organized chemistry" may lead to enhanced polymerization efficiency which in turn is expected to facilitate the road towards a self-replicating chemical system based on all four nucleic acid bases.

  20. Development and assessment of a chemistry-based computer video game as a learning tool

    NASA Astrophysics Data System (ADS)

    Martinez-Hernandez, Kermin Joel

    The chemistry-based computer video game is a multidisciplinary collaboration between chemistry and computer graphics and technology fields developed to explore the use of video games as a possible learning tool. This innovative approach aims to integrate elements of commercial video game and authentic chemistry context environments into a learning experience through gameplay. The project consists of three areas: development, assessment, and implementation. However, the foci of this study were the development and assessment of the computer video game including possible learning outcomes and game design elements. A chemistry-based game using a mixed genre of a single player first-person game embedded with action-adventure and puzzle components was developed to determine if students' level of understanding of chemistry concepts change after gameplay intervention. Three phases have been completed to assess students' understanding of chemistry concepts prior and after gameplay intervention. Two main assessment instruments (pre/post open-ended content survey and individual semi-structured interviews) were used to assess student understanding of concepts. In addition, game design elements were evaluated for future development phases. Preliminary analyses of the interview data suggest that students were able to understand most of the chemistry challenges presented in the game and the game served as a review for previously learned concepts as well as a way to apply such previous knowledge. To guarantee a better understanding of the chemistry concepts, additions such as debriefing and feedback about the content presented in the game seem to be needed. The use of visuals in the game to represent chemical processes, game genre, and game idea appear to be the game design elements that students like the most about the current computer video game.

  1. 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.

  2. Synthesis of new kojic acid based unnatural α-amino acid derivatives.

    PubMed

    Balakrishna, C; Payili, Nagaraju; Yennam, Satyanarayana; Devi, P Uma; Behera, Manoranjan

    2015-11-01

    An efficient method for the preparation of kojic acid based α-amino acid derivatives by alkylation of glycinate schiff base with bromokojic acids have been described. Using this method, mono as well as di alkylated kojic acid-amino acid conjugates have been prepared. This is the first synthesis of C-linked kojic acid-amino acid conjugate where kojic acid is directly linked to amino acid through a C-C bond.

  3. Uncertainty quantification and integration of machine learning techniques for predicting acid rock drainage chemistry: a probability bounds approach.

    PubMed

    Betrie, Getnet D; Sadiq, Rehan; Morin, Kevin A; Tesfamariam, Solomon

    2014-08-15

    Acid rock drainage (ARD) is a major pollution problem globally that has adversely impacted the environment. Identification and quantification of uncertainties are integral parts of ARD assessment and risk mitigation, however previous studies on predicting ARD drainage chemistry have not fully addressed issues of uncertainties. In this study, artificial neural networks (ANN) and support vector machine (SVM) are used for the prediction of ARD drainage chemistry and their predictive uncertainties are quantified using probability bounds analysis. Furthermore, the predictions of ANN and SVM are integrated using four aggregation methods to improve their individual predictions. The results of this study showed that ANN performed better than SVM in enveloping the observed concentrations. In addition, integrating the prediction of ANN and SVM using the aggregation methods improved the predictions of individual techniques.

  4. The Chemistry of Fitness. Active Activities.

    ERIC Educational Resources Information Center

    Bergandine, David R.; And Others

    1991-01-01

    The outline for a unit on the chemistry of fitness and nutrition is presented. Topics discussed include the organic basis of life, functional groups, kitchen experiments, micronutrients, energetics, fitness vs. fatness, current topics, and evaluation. This unit reviews the basic concepts of chemical bonding, acid-base chemistry, stoichiometry, and…

  5. Arsenic-Dominated Chemistry in the Acid Cleaning of InGaAs and InAlAs Surfaces

    SciTech Connect

    Sun, Y.; Pianetta, P.; Chen, P.-T.; Kobayashi, M.; Nishi, Y.; Goel, N.; Garner, M.; Tsai, W.

    2008-10-31

    The surface cleaning of InGaAs and InAlAs is studied using Synchrotron Radiation Photoelectron Spectroscopy. Thermal annealing at 400 C can not completely remove the native oxides from those surfaces. Elemental arsenic build-up is observed on both surfaces after acid treatment using HCl, HF or H{sub 2}SO{sub 4} solutions, which is similar to acid-cleaned GaAs surface. Cleaned InGaAs surface is oxide free but small amount of aluminum oxide remains on cleaned InAlAs surface. The common chemical reactions between III-As semiconductors and acid solutions are identified and are found to be dominated by arsenic chemistry.

  6. Computer-based, Jeopardy™-like game in general chemistry for engineering majors

    NASA Astrophysics Data System (ADS)

    Ling, S. S.; Saffre, F.; Kadadha, M.; Gater, D. L.; Isakovic, A. F.

    2013-03-01

    We report on the design of Jeopardy™-like computer game for enhancement of learning of general chemistry for engineering majors. While we examine several parameters of student achievement and attitude, our primary concern is addressing the motivation of students, which tends to be low in a traditionally run chemistry lectures. The effect of the game-playing is tested by comparing paper-based game quiz, which constitutes a control group, and computer-based game quiz, constituting a treatment group. Computer-based game quizzes are Java™-based applications that students run once a week in the second part of the last lecture of the week. Overall effectiveness of the semester-long program is measured through pretest-postest conceptual testing of general chemistry. The objective of this research is to determine to what extent this ``gamification'' of the course delivery and course evaluation processes may be beneficial to the undergraduates' learning of science in general, and chemistry in particular. We present data addressing gender-specific difference in performance, as well as background (pre-college) level of general science and chemistry preparation. We outline the plan how to extend such approach to general physics courses and to modern science driven electives, and we offer live, in-lectures examples of our computer gaming experience. We acknowledge support from Khalifa University, Abu Dhabi

  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. Studies related to primitive chemistry. A proton and nitrogen-14 nuclear magnetic resonance amino acid and nucleic acid constituents and a and their possible relation to prebiotic

    NASA Technical Reports Server (NTRS)

    Manatt, S. L.; Cohen, E. A.; Shiller, A. M.; Chan, S. I.

    1973-01-01

    Preliminary proton nuclear magnetic resonance (NMR) studies were made to determine the applicability of this technique for the study of interactions between monomeric and polymeric amino acids with monomeric nucleic acid bases and nucleotides. Proton NMR results for aqueous solutions (D2O) demonstrated interactions between the bases cytosine and adenine and acidic and aromatic amino acids. Solutions of 5'-AMP admixed with amino acids exhibited more complex behavior but stacking between aromatic rings and destacking at high amino acids concentration was evident. The multisite nature of 5'-AMP was pointed out. Chemical shift changes for adenine and 5'-AMP with three water soluble polypeptides demonstrated that significant interactions exist. It was found that the linewidth-pH profile of each amino acid is unique. It is concluded that NMR techniques can give significant and quantitative data on the association of amino acid and nucleic acid constituents.

  9. Effects of storm runoff on acid-base accounting of mine drainage

    SciTech Connect

    Sjoegren, D.R.; Olyphant, G.A.; Harper, D.

    1997-12-31

    Pre-reclamation conditions were documented at an abandoned mine site in an upland area at the headwaters of a small perennial stream in southwestern Indiana. Stream discharge and chemistry were monitored from April to October 1995, in an effort to assess the total acid-base budget of outflows from the site. The chemistry of three lakes, a shallow aquifer, and flooded mine voids was also monitored. During the period of monitoring, thirty-five rainfall-runoff events occurred, producing a total storm discharge of approximately 6.12 x 10{sup 7} L. Baseflow during the monitoring period was approximately 1.10 x 10{sup 8} L and was characterized by water chemistry that was similar to that of a spring that issued from the flooded mine voids. Analysis of the discharge and chemistry associated with an isolated thunderstorm revealed fluctuations in acidity that were not congruent with fluctuations in the total discharge hydrograph. For example, acidity increased rapidly during the initial phase of hydrograph rise, but dropped significantly as the storm hydrograph peaked. A second, more subdued, rise in acidity occurred during a second rain pulse, and the acidity gradually decreased to pre-storm levels during hydrograph recession. The trends are interpreted to reflect different sources of storm runoff associated with various components of the total discharge hydrograph. Preliminary calculations indicate that the total quantity of acidity that is discharged during stormflow is about eight times higher than that which is discharged during a comparable period under baseflow conditions. While the lower acid concentrations generated during storm events are ecologically favorable, the increase in total quantities of acidity can have implications for the buffering capacities of receiving water bodies.

  10. Cirrus cloud mimic surfaces in the laboratory: organic acids, bases and NOx heterogeneous reactions

    NASA Astrophysics Data System (ADS)

    Sodeau, J.; Oriordan, B.

    2003-04-01

    CIRRUS CLOUD MIMIC SURFACES IN THE LABORATORY:ORGANIC ACIDS, BASES AND NOX HETEROGENEOUS REACTIONS. B. ORiordan, J. Sodeau Department of Chemistry and Environment Research Institute, University College Cork, Ireland j.sodeau@ucc.ie /Fax: +353-21-4902680 There are a variety of biogenic and anthropogenic sources for the simple carboxylic acids to be found in the troposphere giving rise to levels as high as 45 ppb in certain urban areas. In this regard it is of note that ants of genus Formica produce some 10Tg of formic acid each year; some ten times that produced by industry. The expected sinks are those generally associated with tropospheric chemistry: the major routes studied, to date, being wet and dry deposition. No studies have been carried out hitherto on the role of water-ice surfaces in the atmospheric chemistry of carboxylic acids and the purpose of this paper is to indicate their potential function in the heterogeneous release of atmospheric species such as HONO. The deposition of formic acid on a water-ice surface was studied using FT-RAIR spectroscopy over a range of temperatures between 100 and 165K. In all cases ionization to the formate (and oxonium) ions was observed. The results were confirmed by TPD (Temperature Programmed Desorption) measurements, which indicated that two distinct surface species adsorb to the ice. Potential reactions between the formic acid/formate ion surface and nitrogen dioxide were subsequently investigated by FT-RAIRS. Co-deposition experiments showed that N2O3 and the NO+ ion (associated with water) were formed as products. A mechanism is proposed to explain these results, which involves direct reaction between the organic acid and nitrogen dioxide. Similar experiments involving acetic acid also indicate ionization on a water-ice surface. The results are put into the context of atmospheric chemistry potentially occuring on cirrus cloud surfaces.

  11. Student Perceptions of Group-Based Competitive Exercises in the Chemistry Classroom

    ERIC Educational Resources Information Center

    Cannon, Kevin C.; Mody, Tina; Breen, Maureen P.

    2008-01-01

    A non-traditional teaching method that can operate as a vehicle for engaging students is group-based competitive exercises. These exercises combine cooperative learning with a competitive environment and may be employed to promote subject- and problem-based learning. Survey responses of college-level organic chemistry and biochemistry students…

  12. Effects of surface chemistry on the optical properties and cellular interaction of lanthanide-based nanoparticles

    NASA Astrophysics Data System (ADS)

    Pedraza, Francisco J.; Avalos, Julio C.; Mimun, Lawrence C.; Yust, Brian G.; Tsin, Andrew; Sardar, Dhiraj K.

    2015-03-01

    Fluorescent nanoparticles (NPs) such as KYb2F7:Tm3+ potential in biomedical applications due to their ability to absorb and emit within the biological window, where near infrared light is less attenuated by soft tissue. This results in less tissue damage and deeper tissue penetration making it a viable candidate in biological imaging. Another big factor in determining their ability to perform in a biological setting is the surface chemistry. Biocompatible coatings, including polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), pluronic and folic acid are commonly used because they pose several advantages such as ease of functionalization, better dispersion, and higher cellular uptake. To study the effects of the NP surface chemistry, KYb2F7:Tm3+ a solvothermal method using PEG, PVP, pluronic acid, and folic acid as a capping agent, followed by thorough optical characterizations. Optical changes were thoroughly studied and compared using absorption, emission, and quantum yield data. Cell viability was obtained by treating Rhesus Monkey Retinal Endothelial cells (RhREC) with KYb2F7:Tm3+ and counting viable cells following a 24 hour uptake period. The work presented will compare the optical properties and toxicity dependency on the surface chemistry on KYb2F7:Tm3+. The results will also indicate that KYb2F7:Tm3+ nanoparticles are viable candidates for various biomedical applications.

  13. Textbook Questions in Context-Based and Traditional Chemistry Curricula Analysed from a Content Perspective and a Learning Activities Perspective

    NASA Astrophysics Data System (ADS)

    Overman, Michelle; Vermunt, Jan D.; Meijer, Paulien C.; Bulte, Astrid M. W.; Brekelmans, Mieke

    2013-11-01

    In this study, questions in context-based and traditional chemistry textbooks were analysed from two perspectives that are at the heart of chemistry curricula reforms: a content perspective and a learning activities perspective. To analyse these textbook questions, we developed an instrument for each perspective. In total, 971 textbook questions were analysed. Textbook questions in context-based and traditional curricula appeared to differ significantly in their orientation on content and in the activation to engage students in certain learning activities. Although traditional curricula included more questions that stress traditional chemistry content and included more reproductive chemistry questions than context-based curricula, they were not always as traditional as we had expected. Context-based chemistry curricula focused more on chemistry content relating to societal/technological issues and chemistry theory development and also more questions were included that activate students to regulate their own learning. However, context-based chemistry curricula still included a considerable amount of traditional chemistry content and did not focus as much on higher order learning as we had expected. The developed instruments might be helpful in chemistry curricula design to gain insights into the content which is stressed and how students are activated by textbook questions to engage in learning.

  14. Students' Understandings of Acid Strength: How Meaningful Is Reliability When Measuring Alternative Conceptions

    ERIC Educational Resources Information Center

    Bretz, Stacey Lowery; McClary, LaKeisha

    2015-01-01

    Most organic chemistry reactions occur by a mechanism that includes acid-base chemistry, so it is important that students develop and learn to use correct conceptions of acids and acid strength. Recent studies have described undergraduate organic chemistry students' cognitive resources related to the Brønsted-Lowry acid model and the Lewis acid…

  15. Instructional Misconceptions in Acid-Base Equilibria: An Analysis from a History and Philosophy of Science Perspective

    NASA Astrophysics Data System (ADS)

    Kousathana, Margarita; Demerouti, Margarita; Tsaparlis, Georgios

    The implications of history and philosophy of chemistry are explored in the context of chemical models. Models and modeling provide the context through which epistemological aspects of chemistry can be promoted. In this work, the development of ideas and models about acids and bases (with emphasis on the Arrhenius, the Brønsted-Lowry, and the Lewis models) are presented. In addition, misconceptions (alternative and instructional ones) on acid-base (ionic) equilibria are examined from the history and philosophy of science perspective. The relation between the development of the models and students misconceptions are investigated. Finally, the hypothesis that history and philosophy could help educators anticipate students misconceptions is examined.

  16. Heterogeneous Chemistry of HONO on Liquid Sulfuric Acid: A New Mechanism of Chlorine Activation on Stratospheric Sulfate Aerosols

    NASA Technical Reports Server (NTRS)

    Zhang, Renyi; Leu, Ming-Taun; Keyser, Leon F.

    1996-01-01

    Heterogeneous chemistry of nitrous acid (HONO) on liquid sulfuric acid (H2SO4) Was investigated at conditions that prevail in the stratosphere. The measured uptake coefficient (gamma) of HONO on H2SO4 increased with increasing acid content, ranging from 0.03 for 65 wt % to about 0.1 for 74 wt %. In the aqueous phase, HONO underwent irreversible reaction with H2SO4 to form nitrosylsulfuric acid (NO(+)HSO4(-). At temperatures below 230 K, NO(+)HSO4(-) was observed to be stable and accumulated in concentrated solutions (less than 70 wt % H2SO4) but was unstable and quickly regenerated HONO in dilute solutions (less than 70 wt %). HCl reacted with HONO dissolved in sulfuric acid, releasing gaseous nitrosyl chloride (ClNO). The reaction probability between HCl and HONO varied from 0.01 to 0.02 for 60-72 wt % H2SO4. In the stratosphere, ClNO photodissociates rapidly to yield atomic chlorine, which catalytically destroys ozone. Analysis of the laboratory data reveals that the reaction of HCl with HONO on sulfate aerosols can affect stratospheric ozone balance during elevated sulfuric acid loadings after volcanic eruptions or due to emissions from the projected high-speed civil transport (HSCT). The present results may have important implications on the assessment of environmental acceptability of HSCT.

  17. Radiation chemistry of amino acids, peptides and proteins in relation to the radiation sterilization of high-protein foods

    SciTech Connect

    Garrison, W. M.

    1981-12-01

    An important source of information on the question of whether or not toxic or other deleterious substances are formed in the radiation sterilization of foods is the chemical study of reaction products and reaction mechanisms in the radiolysis of individual food components. The present evaluation of the radiation chemistry of amino acids, peptides, and proteins outlines the various radiation-induced processes which lead to amino acid degradation and to the synthesis of amino acid derivatives of higher molecular weight. Among the latter are the ..cap alpha..,..cap alpha..'-diamino dicarboxylic acids which are formed as major products in the radiolysis of peptides both in aqueous solution and in the solid state. The ..cap alpha..,..cap alpha..'-diamino acids are of particular interest as irradiation products because they represent a class of compounds not normally encountered in plant and animal protein sources. Such compounds have, however, been isolated from certain types of bacteria and bacterial products. All of the available data strongly suggest that the ..cap alpha..,..cap alpha..'-diamino acids are produced in significant yield in the radiation sterilization of high protein foods. The importance of initiating extensive chemical and biological studies of these and of other high molecular weight products in irradiated food is emphasized.

  18. The coordination chemistry of tartronic acid with copper: magnetic studies of a quasi-equilateral tricopper triangle.

    PubMed

    Pascu, Gabriel; Deville, Claire; Clifford, Sarah E; Guenée, Laure; Besnard, Céline; Krämer, Karl W; Liu, Shi-Xia; Decurtins, Silvio; Tuna, Floriana; McInnes, Eric J L; Winpenny, Richard E P; Williams, Alan F

    2014-01-14

    The coordination chemistry of tartronic acid, , with copper(ii) has been investigated. Structures of two complexes are reported containing respectively the complex [Cu(-2H)2Cl](3-) where acts as a bidentate ligand through carboxylates, and [Cu3(-3H)3](3-) where the alcohol function is deprotonated to bridge two coppers in a triangular trinuclear complex. The latter species undergoes facile oxidation leading to carbon-carbon bond formation. The magnetic and EPR properties of the trinuclear complex have been studied in detail.

  19. Carbohydrate-based bioactive compounds for medicinal chemistry applications.

    PubMed

    Cipolla, L; Peri, F

    2011-01-01

    In this article we review our work over the years on carbohydrates and carbohydrate mimetics and their applications in medicinal chemistry. In the first part of the review innovative synthetic methods, such as the chemoselective glycosylation method originally developed by our group and its applications to the synthesis of neoglycoconjugates (neoglycopeptides, oligosaccharide mimetics, neoglycolipids, etc…) will be presented. The high density of functional groups (hydroxyls) on the monosaccharides and the structural role of sugars forming the core of complex glycans in scaffolding and orienting the external sugar units for the interaction with receptors, inspired us and others to use sugars as scaffolds for the construction of pharmacologically active compounds. In the second part of this review, we will present some examples of bioactive and pharmacologically active compounds obtained by decorating monosaccharide scaffolds with pharmacophore groups. Sugar-derived protein ligands were also used as chemical probes to study the interaction of their target with other proteins in the cell. In this context, sugar mimetics and sugar-derived compounds have been employed as tools for exploring biology according to the "chemical genetic" approach.

  20. Using Laboratory Activities Enhanced with Concept Cartoons to Support Progression in Students' Understanding of Acid-Base Concepts

    ERIC Educational Resources Information Center

    Ozmen, Haluk; Demircioglu, Gokhan; Burhan, Yasemin; Naseriazar, Akbar; Demircioglu, Hulya

    2012-01-01

    The aim of this study is to examine the effectiveness of an intervention based on a series of laboratory activities enhanced with concept cartoons. The purpose of the intervention was to enhance students' understanding of acid-base chemistry for eight grade students' from two classes in a Turkish primary school. A pretest-posttest non-equivalent…

  1. D-erythroascorbic acid: Its preparations, chemistry, and metabolism (fungi and plants)

    SciTech Connect

    Loewus, F.A. . Inst. of Biological Chemistry); Seib, P.A. . Dept. of Grain Science and Industry)

    1991-01-01

    The origin of oxalate in plants has received considerable attention and glycolate metabolism has been generally regarded as a prime precursor candidate although studies on the metabolism of L-ascorbic acid single out that plant constituent as well. Experiments with oxalate-accumulating plants that contain little or no tartaric acid revealed the presence of a comparable L-ascorbic acid metabolism with the exception that the cleavage products were oxalic acid and L-threonic acid or products of L-threonic acid metabolism. A reasonable mechanism for cleavage of L-ascorbic acid at the endiolic bond is found in studies on the photooxygenation of L-ascorbic acid. Presumably, analogs of L-ascorbic acid that differ only in the substituent at C4 also form a hydroperoxide in the presence of alkaline hydrogen peroxide and subsequently yield oxalic acid and the corresponding aldonic acid or its lactone. We became interested in such a possibility when we discovered that L-ascorbic acid was rare or absent in certain yeasts and fungi whereas a L-ascorbic acid analog, D-glycero-pent-2-enono- 1,4-lactone (D-erythroascorbic acid), was present. It has long been known that oxalate occurs in yeasts and fungi and its production plays a role in plant pathogenesis. As to the biosynthetic origin of fungal oxalic acid there is little information although it is generally assumed that oxaloacetate or possibly, glycolate, might be that precursor.

  2. D-erythroascorbic acid: Its preparations, chemistry, and metabolism (fungi and plants). Final report

    SciTech Connect

    Loewus, F.A.; Seib, P.A.

    1991-12-31

    The origin of oxalate in plants has received considerable attention and glycolate metabolism has been generally regarded as a prime precursor candidate although studies on the metabolism of L-ascorbic acid single out that plant constituent as well. Experiments with oxalate-accumulating plants that contain little or no tartaric acid revealed the presence of a comparable L-ascorbic acid metabolism with the exception that the cleavage products were oxalic acid and L-threonic acid or products of L-threonic acid metabolism. A reasonable mechanism for cleavage of L-ascorbic acid at the endiolic bond is found in studies on the photooxygenation of L-ascorbic acid. Presumably, analogs of L-ascorbic acid that differ only in the substituent at C4 also form a hydroperoxide in the presence of alkaline hydrogen peroxide and subsequently yield oxalic acid and the corresponding aldonic acid or its lactone. We became interested in such a possibility when we discovered that L-ascorbic acid was rare or absent in certain yeasts and fungi whereas a L-ascorbic acid analog, D-glycero-pent-2-enono- 1,4-lactone (D-erythroascorbic acid), was present. It has long been known that oxalate occurs in yeasts and fungi and its production plays a role in plant pathogenesis. As to the biosynthetic origin of fungal oxalic acid there is little information although it is generally assumed that oxaloacetate or possibly, glycolate, might be that precursor.

  3. Developing and Implementing a Reorganized Undergraduate Chemistry Curriculum Based on the Foundational Chemistry Topics of Structure, Reactivity, and Quantitation

    ERIC Educational Resources Information Center

    Schaller, Chris P.; Graham, Kate J.; Johnson, Brian J.; Fazal, M. A.; Jones, T. Nicholas; McIntee, Edward J.; Jakubowski, Henry V.

    2014-01-01

    The recent revision of undergraduate curricular guidelines from the American Chemical Society Committee on Professional Training (ACS-CPT) has generated interest in examining new ways of organizing course sequences both for chemistry majors and for nonmajors. A radical reconstruction of the foundation-level chemistry curriculum is presented in…

  4. Beyond Problem-Based Learning: Using Dynamic PBL in Chemistry

    ERIC Educational Resources Information Center

    Overton, Tina L.; Randles, Christopher A.

    2015-01-01

    This paper describes the development and implementation of a novel pedagogy, dynamic problem-based learning. The pedagogy utilises real-world problems that evolve throughout the problem-based learning activity and provide students with choice and different data sets. This new dynamic problem-based learning approach was utilised to teach…

  5. Testing the Potential for Computational Chemistry to Quantify Biophysical Properties of the Non-Proteinaceous Amino Acids

    NASA Astrophysics Data System (ADS)

    Lu, Yi; Freeland, Stephen

    2006-08-01

    Although most proteins of most living organisms are constructed from the same set of 20 amino acids, all indications are that this standard alphabet represents a mere subset of what was available to life during early evolution. However, we currently lack an appropriate quantitative framework with which to test the qualitative hypotheses that have been offered to date as explanations for nature's "choices." Specifically, although many indices have been developed to describe the 20 standard amino acids, few or no comparable data extend to prebiotically plausible alternatives because of the costly and time-consuming bench experiments that would be required. Computational chemistry (specifically quantitative structure property relationship methods) offers a potentially fast, cost-effective remedy for this knowledge gap by predicting such molecular properties in silico. Thus, we investigated the use of various freely accessible programs to predict three key amino acid properties (hydrophobicity, charge, and size). We assessed the accuracy of these predictions by comparisons with experimentally determined counterparts for appropriate test data sets. In light of these results, and factors of software accessibility and transparency, we suggest a method for further computational assessments of prebiotically plausible amino acids. The results serve as a starting point for future quantitative analysis of amino acid alphabet evolution.

  6. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  7. Heterogeneous Chemistry of HO2NO2 on Liquid Sulfuric Acid

    NASA Technical Reports Server (NTRS)

    Leu, Ming-Taun

    1995-01-01

    The interaction of HO2NO2 (peroxynitric acid, PNA) vapor with liquid sulfuric acid surfaces was investigated for the acid contents ranging from 50 to 70 wt % and over a temperature range from 205 to 230 K, using a fast flow-reactor coupled to a chemical ionization mass spectrometer. PNA was observed to be physically taken up by liquid sulfuric acid, without undergoing irreversible aqueous phase reactions.

  8. 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

  9. Observations of formic and acetic acid by chemical ionization mass spectrometry in the Deep Convective Clouds and Chemistry Experiment

    NASA Astrophysics Data System (ADS)

    Treadaway, V.; McNeill, A.; Heikes, B.; O'Sullivan, D. W.; Silwal, I.

    2013-12-01

    Formic (HFo) and acetic acid (HAc) are part of the atmospheric processing of carbon and their measurement is relevant to defining oxygenated volatile organic carbon (OVOC) emissions, to examining photochemical processing of volatile organic carbon (VOC) and OVOCs, and to the photochemical processing of organic aerosol. Further, they can serve as photochemical tracers of convective transport, cloud chemical processes, and precipitation scavenging. The addition of HFo and HAc measurements to the Deep Convective Clouds and Chemistry Experiment (DC3) is relevant to the DC3 science objectives and complements the suite of chemicals already observed during DC3. The peroxide chemical ionization mass spectrometer (PCIMS) was flown aboard the NCAR Gulfstream-V platform in DC3 and while its primary function was to observe hydrogen peroxide and methylhydroperoxide it recorded signals attributed to iodide cluster ions of HFo and HAc at mass-charge ratios of 173 and 187, respectively. Post-mission laboratory experiments were performed to determine the CIMS instrument's sensitivity to these acids under the varying water vapor and sample flow conditions encountered during DC3 flights. The results of field measurements, laboratory experiments and the HFo and HAc recovery process are reported and HFo and HAc measurement quality assessed. The resultant HFo and HAc data are presented and interpreted with respect to atmospheric chemistry within measurement constraints. The DC3 observations were made in May and June 2012 and extended from the surface to 13 km over the central United States.

  10. Recent Applications of Carbon-Based Nanomaterials in Analytical Chemistry: Critical Review

    PubMed Central

    Scida, Karen; Stege, Patricia W.; Haby, Gabrielle; Messina, Germán A.; García, Carlos D.

    2011-01-01

    The objective of this review is to provide a broad overview of the advantages and limitations of carbon-based nanomaterials with respect to analytical chemistry. Aiming to illustrate the impact of nanomaterials on the development of novel analytical applications, developments reported in the 2005–2010 period have been included and divided into sample preparation, separation, and detection. Within each section, fullerenes, carbon nanotubes, graphene, and composite materials will be addressed specifically. Although only briefly discussed, included is a section highlighting nanomaterials with interesting catalytic properties that can be used in the design of future devices for analytical chemistry. PMID:21458626

  11. Recent applications of carbon-based nanomaterials in analytical chemistry: critical review.

    PubMed

    Scida, Karen; Stege, Patricia W; Haby, Gabrielle; Messina, Germán A; García, Carlos D

    2011-04-08

    The objective of this review is to provide a broad overview of the advantages and limitations of carbon-based nanomaterials with respect to analytical chemistry. Aiming to illustrate the impact of nanomaterials on the development of novel analytical applications, developments reported in the 2005-2010 period have been included and divided into sample preparation, separation, and detection. Within each section, fullerenes, carbon nanotubes, graphene, and composite materials will be addressed specifically. Although only briefly discussed, included is a section highlighting nanomaterials with interesting catalytic properties that can be used in the design of future devices for analytical chemistry.

  12. Island Explorations: Discovering Effects of Environmental Research-Based Lab Activities on Analytical Chemistry Students

    ERIC Educational Resources Information Center

    Tomasik, Janice Hall; LeCaptain, Dale; Murphy, Sarah; Martin, Mary; Knight, Rachel M.; Harke, Maureen A.; Burke, Ryan; Beck, Kara; Acevedo-Polakovich, I. David

    2014-01-01

    Motivating students in analytical chemistry can be challenging, in part because of the complexity and breadth of topics involved. Some methods that help encourage students and convey real-world relevancy of the material include incorporating environmental issues, research-based lab experiments, and service learning projects. In this paper, we…

  13. Incorporating Course-Based Undergraduate Research Experiences into Analytical Chemistry Laboratory Curricula

    ERIC Educational Resources Information Center

    Kerr, Melissa A.; Yan, Fei

    2016-01-01

    A continuous effort within an undergraduate university setting is to improve students' learning outcomes and thus improve students' attitudes about a particular field of study. This is undoubtedly relevant within a chemistry laboratory. This paper reports the results of an effort to introduce a problem-based learning strategy into the analytical…

  14. Computer Based Instructional Techniques in Undergraduate Introductory Organic Chemistry: Rationale, Developmental Techniques, Programming Strategies and Evaluation.

    ERIC Educational Resources Information Center

    Culp, G. H.; And Others

    Over 100 interactive computer programs for use in general and organic chemistry at the University of Texas at Austin have been prepared. The rationale for the programs is based upon the belief that computer-assisted instruction (CAI) can improve education by, among other things, freeing teachers from routine tasks, measuring entry skills,…

  15. Developing Web-Based, Pedagogical Content Coursework for High School Chemistry Teachers

    NASA Astrophysics Data System (ADS)

    Brooks, David W.; Markwell, John P.; Langell, Marjorie A.; Emry, Randall; Crippen, Kent J.; Brooks, Helen B.; Abuloum, Amjad; Cohen, Karen C.

    2007-11-01

    We report on the creation and delivery of Web-based content courses stressing content integration for high school chemistry teachers. We make recommendations to other chemical educators seeking to develop instructional systems that emphasize automatic, repeatable, practice with immediate, performance-related feedback.

  16. Infrared and Raman Spectroscopy: A Discovery-Based Activity for the General Chemistry Curriculum

    ERIC Educational Resources Information Center

    Borgsmiller, Karen L.; O'Connell, Dylan J.; Klauenberg, Kathryn M.; Wilson, Peter M.; Stromberg, Christopher J.

    2012-01-01

    A discovery-based method is described for incorporating the concepts of IR and Raman spectroscopy into the general chemistry curriculum. Students use three sets of springs to model the properties of single, double, and triple covalent bonds. Then, Gaussian 03W molecular modeling software is used to illustrate the relationship between bond…

  17. Integration of Information Literacy Components into a Large First-Year Lecture-Based Chemistry Course

    ERIC Educational Resources Information Center

    Locknar, Angela; Mitchell, Rudolph; Rankin, Janet; Sadoway, Donald R.

    2012-01-01

    A first-year chemistry course is ideal for introducing students to finding and using scholarly information early in their academic careers. A four-pronged approach (lectures, homework problems, videos, and model solutions) was used to incorporate library research skills into a large lecture-based course. Pre- and post-course surveying demonstrated…

  18. Creative Uses for Calculator-based Laboratory (CBL) Technology in Chemistry.

    ERIC Educational Resources Information Center

    Sales, Cynthia L.; Ragan, Nicole M.; Murphy, Maureen Kendrick

    1999-01-01

    Reviews three projects that use a graphing calculator linked to a calculator-based laboratory device as a portable data-collection system for students in chemistry classes. Projects include Isolation, Purification and Quantification of Buckminsterfullerene from Woodstove Ashes; Determination of the Activation Energy Associated with the…

  19. Self-Directed Activity-Based Learning and Achievement in High School Chemistry

    ERIC Educational Resources Information Center

    Bassett, Meighan M.; Martinez, James; Martin, Ellice P.

    2014-01-01

    The effects of student-directed activity-based learning (SDABL) were examined in two high school chemistry classes. Students in the SDABL class were given pretest results, a list of standards to be mastered, and a chart of learning activities categorized by difficulty level. They selected activities to meet their needs and preferences.…

  20. Evaluating a Professional Development Framework to Empower Chemistry Teachers to Design Context-Based Education

    ERIC Educational Resources Information Center

    Stolk, Machiel Johan; Bulte, Astrid; De Jong, Onno; Pilot, Albert

    2012-01-01

    Even experienced chemistry teachers require professional development when they are encouraged to become actively engaged in the design of new context-based education. This study briefly describes the development of a framework consisting of goals, learning phases, strategies and instructional functions, and how the framework was translated into a…

  1. A Learning-Cycle-Based Organic Chemistry Laboratory Program for Students in Dietetics.

    ERIC Educational Resources Information Center

    Mueller, William J.

    1982-01-01

    The laboratory of an organic chemistry course for dietetics students is based on the learning cycle approach (exploration, invention-concept introduction, and concept application). The laboratory program is divided into four sections: lab techniques, compound types, reaction types, and reaction characteristics. (SK)

  2. Addition of a Project-Based Component to a Conventional Expository Physical Chemistry Laboratory

    ERIC Educational Resources Information Center

    Tsaparlis, Georgios; Gorezi, Marianna

    2007-01-01

    Students should enjoy their laboratory classes and for this purpose a project-based activity is added to a conventional physical chemistry laboratory. Students were given project work instead of conventional experiment and then they had to make progress in the project according to instructions and then carry out experiments related to the project.

  3. A Game-Based Approach to an Entire Physical Chemistry Course

    ERIC Educational Resources Information Center

    Daubenfeld, Thorsten; Zenker, Dietmar

    2015-01-01

    We designed, implemented, and evaluated a game-based learning approach to increase student motivation and achievement for an undergraduate physical chemistry course. By focusing only on the most important game aspects, the implementation was realized with a production ratio of 1:8 (study load in hours divided by production effort in hours).…

  4. "Chemistry Is in the News": Taxonomy of Authentic News Media-Based Learning Activities. Research Report

    ERIC Educational Resources Information Center

    Glaser, Rainer E.; Carson, Kathleen M.

    2005-01-01

    A brief history is given of approaches that aim at achieving a connectedness of the content of organic chemistry courses to real world issues. Recently, such approaches have relied more and more on online media resources, the tools of the Internet and the World Wide Web. We propose a six-level taxonomy of 'authentic news media-based learning…

  5. Effect of Problem-Based Learning on Students' Achievement in Chemistry

    ERIC Educational Resources Information Center

    Aidoo, Benjamin; Boateng, Sampson Kwadwo; Kissi, Philip Siaw; Ofori, Isaac

    2016-01-01

    The study investigated the effect of problem-based learning (PBL) on students' achievement in chemistry. Learners' low achievement in Science in South Africa has been a concern to government, stakeholders, school principals and parents over the years as a result of poor teaching techniques, students' attitudes, lack of teaching and learning…

  6. Problem-Based Learning Method: Secondary Education 10th Grade Chemistry Course Mixtures Topic

    ERIC Educational Resources Information Center

    Üce, Musa; Ates, Ismail

    2016-01-01

    In this research; aim was determining student achievement by comparing problem-based learning method with teacher-centered traditional method of teaching 10th grade chemistry lesson mixtures topic. Pretest-posttest control group research design is implemented. Research sample includes; two classes of (total of 48 students) an Anatolian High School…

  7. Enhancing Undergraduate Students' Chemistry Understanding through Project-Based Learning in an IT Environment

    ERIC Educational Resources Information Center

    Barak, Miri; Dori, Yehudit Judy

    2005-01-01

    Project-based learning (PBL), which is increasingly supported by information technologies (IT), contributes to fostering student-directed scientific inquiry of problems in a real-world setting. This study investigated the integration of PBL in an IT environment into three undergraduate chemistry courses, each including both experimental and…

  8. Team-Based Learning Reduces Attrition in a First-Semester General Chemistry Course

    ERIC Educational Resources Information Center

    Comeford, Lorrie

    2016-01-01

    Team-based learning (TBL) is an instructional method that has been shown to reduce attrition and increase student learning in a number of disciplines. TBL was implemented in a first-semester general chemistry course, and its effect on attrition was assessed. Attrition from sections before implementing TBL (fall 2008 to fall 2009) was compared with…

  9. Structurally Based Therapeutic Evaluation: A Therapeutic and Practical Approach to Teaching Medicinal Chemistry.

    ERIC Educational Resources Information Center

    Alsharif, Naser Z.; And Others

    1997-01-01

    Explains structurally based therapeutic evaluation of drugs, which uses seven therapeutic criteria in translating chemical and structural knowledge into therapeutic decision making in pharmaceutical care. In a Creighton University (Nebraska) medicinal chemistry course, students apply the approach to solve patient-related therapeutic problems in…

  10. Enquiry-Based Learning: Experiences of First Year Chemistry Students Learning Spectroscopy

    ERIC Educational Resources Information Center

    Lucas, Timothy; Rowley, Natalie M.

    2011-01-01

    We explored the experiences of first year chemistry students of an Enquiry-Based Learning (EBL) approach to learning spectroscopy. An investigation of how students' perceived confidences changed as a result of their experience of using EBL in the spectroscopy course was carried out. Changes in the students' perceived confidence, both in their…

  11. Transitioning from Expository Laboratory Experiments to Course-Based Undergraduate Research in General Chemistry

    ERIC Educational Resources Information Center

    Clark, Ted M.; Ricciardo, Rebecca; Weaver, Tyler

    2016-01-01

    General chemistry courses predominantly use expository experiments that shape student expectations of what a laboratory activity entails. Shifting within a semester to course-based undergraduate research activities that include greater decision-making, collaborative work, and "messy" real-world data necessitates a change in student…

  12. Formalizing the First Day in an Organic Chemistry Laboratory Using a Studio-Based Approach

    ERIC Educational Resources Information Center

    Collison, Christina G.; Cody, Jeremy; Smith, Darren; Swartzenberg, Jennifer

    2015-01-01

    A novel studio-based lab module that incorporates student-centered activities was designed and implemented to introduce second-year undergraduate students to the first-semester organic chemistry laboratory. The "First Day" studio module incorporates learning objectives for the course, lab safety, and keeping a professional lab notebook.

  13. A Wiki-Based Group Project in an Inorganic Chemistry Foundation Course

    ERIC Educational Resources Information Center

    Kristian, Kathleen E.

    2015-01-01

    A semester-long group project that utilizes wiki sites to enhance collaboration was developed for a foundation course in inorganic chemistry. Through structured assignments, student groups use metal-based or metal-combating therapeutic agents as a model for applying and understanding course concepts; they also gain proficiency with scientific- and…

  14. How do video-based demonstration assessment tasks affect problem-solving process, test anxiety, chemistry anxiety and achievement in general chemistry students?

    NASA Astrophysics Data System (ADS)

    Terrell, Rosalind Stephanie

    2001-12-01

    Because paper-and-pencil testing provides limited knowledge about what students know about chemical phenomena, we have developed video-based demonstrations to broaden measurement of student learning. For example, students might be shown a video demonstrating equilibrium shifts. Two methods for viewing equilibrium shifts are changing the concentration of the reactants and changing the temperature of the system. The students are required to combine the data collected from the video and their knowledge of chemistry to determine which way the equilibrium shifts. Video-based demonstrations are important techniques for measuring student learning because they require students to apply conceptual knowledge learned in class to a specific chemical problem. This study explores how video-based demonstration assessment tasks affect problem-solving processes, test anxiety, chemistry anxiety and achievement in general chemistry students. Several instruments were used to determine students' knowledge about chemistry, students' test and chemistry anxiety before and after treatment. Think-aloud interviews were conducted to determine students' problem-solving processes after treatment. The treatment group was compared to a control group and a group watching video demonstrations. After treatment students' anxiety increased and achievement decreased. There were also no significant differences found in students' problem-solving processes following treatment. These negative findings may be attributed to several factors that will be explored in this study.

  15. Computational chemistry for graphene-based energy applications: progress and challenges

    NASA Astrophysics Data System (ADS)

    Hughes, Zak E.; Walsh, Tiffany R.

    2015-04-01

    Research in graphene-based energy materials is a rapidly growing area. Many graphene-based energy applications involve interfacial processes. To enable advances in the design of these energy materials, such that their operation, economy, efficiency and durability is at least comparable with fossil-fuel based alternatives, connections between the molecular-scale structure and function of these interfaces are needed. While it is experimentally challenging to resolve this interfacial structure, molecular simulation and computational chemistry can help bridge these gaps. In this Review, we summarise recent progress in the application of computational chemistry to graphene-based materials for fuel cells, batteries, photovoltaics and supercapacitors. We also outline both the bright prospects and emerging challenges these techniques face for application to graphene-based energy materials in future.

  16. Computational chemistry for graphene-based energy applications: progress and challenges.

    PubMed

    Hughes, Zak E; Walsh, Tiffany R

    2015-04-28

    Research in graphene-based energy materials is a rapidly growing area. Many graphene-based energy applications involve interfacial processes. To enable advances in the design of these energy materials, such that their operation, economy, efficiency and durability is at least comparable with fossil-fuel based alternatives, connections between the molecular-scale structure and function of these interfaces are needed. While it is experimentally challenging to resolve this interfacial structure, molecular simulation and computational chemistry can help bridge these gaps. In this Review, we summarise recent progress in the application of computational chemistry to graphene-based materials for fuel cells, batteries, photovoltaics and supercapacitors. We also outline both the bright prospects and emerging challenges these techniques face for application to graphene-based energy materials in future.

  17. Evaluating a Professional Development Framework to Empower Chemistry Teachers to Design Context-Based Education

    NASA Astrophysics Data System (ADS)

    Stolk, Machiel Johan; Bulte, Astrid; De Jong, Onno; Pilot, Albert

    2012-07-01

    Even experienced chemistry teachers require professional development when they are encouraged to become actively engaged in the design of new context-based education. This study briefly describes the development of a framework consisting of goals, learning phases, strategies and instructional functions, and how the framework was translated into a professional development programme intended to empower teachers to design context-based chemistry education. The programme consists of teaching a pre-developed context-based unit, followed by teachers designing an outline of a new context-based unit. The study investigates the process of teacher empowerment during the implementation of the programme. Data were obtained from meetings, classroom discussions and observations. The findings indicated that teachers became empowered to design new context-based units provided they had sufficient time and resources. The contribution of the framework to teacher empowerment is discussed.

  18. Chemistry and applications of organotin(IV) complexes of Schiff bases.

    PubMed

    Nath, Mala; Saini, Pramendra K

    2011-07-21

    Schiff bases are the most widely used versatile ligands, able to coordinate many elements and to stabilize them in various oxidation states. Recently, this class of compounds has been employed as models for biological systems, and in control of stereochemistry in six-coordinate transition metal complexes. Recently, the chemistry of organotin(IV) complexes of Schiff bases has also stemmed from their antitumour, antimicrobial, antinematicidal, anti-insecticidal and anti-inflammatory activities. Furthermore, organotin(IV) complexes of Schiff bases present a wide variety of interesting structural possibilities. Both aliphatic and aromatic Schiff bases in their neutral and deprotonated forms have been used to yield adducts and chelates with variable stoichiometry and different modes of coordination. This critical review (>155 references) focuses upon the chemistry and biological applications of organotin(IV) complexes of Schiff bases reported in the past 15 years. Thermal behavior of these complexes is also discussed.

  19. Functional surface chemistry of carbon-based nanostructures

    NASA Astrophysics Data System (ADS)

    Abdula, Daner

    The recently discovered abilities to synthesize single-walled carbon nanotubes and prepare single layer graphene have spurred interest in these sp2-bonded carbon nanostructures. In particular, studies of their potential use in electronic devices are many as silicon integrated circuits are encountering processing limitations, quantum effects, and thermal management issues due to rapid device scaling. Nanotube and graphene implementation in devices does come with significant hurdles itself. Among these issues are the ability to dope these materials and understanding what influences defects have on expected properties. Because these nanostructures are entirely all-surface, with every atom exposed to ambient, introduction of defects and doping by chemical means is expected to be an effective route for addressing these issues. Raman spectroscopy has been a proven characterization method for understanding vibrational and even electronic structure of graphene, nanotubes, and graphite, especially when combined with electrical measurements, due to a wealth of information contained in each spectrum. In Chapter 1, a discussion of the electronic structure of graphene is presented. This outlines the foundation for all sp2-bonded carbon electronic properties and is easily extended to carbon nanotubes. Motivation for why these materials are of interest is readily gained. Chapter 2 presents various synthesis/preparation methods for both nanotubes and graphene, discusses fabrication techniques for making devices, and describes characterization methods such as electrical measurements as well as static and time-resolved Raman spectroscopy. Chapter 3 outlines changes in the Raman spectra of individual metallic single-walled carbon nantoubes (SWNTs) upon sidewall covalent bond formation. It is observed that the initial degree of disorder has a strong influence on covalent sidewall functionalization which has implications on developing electronically selective covalent chemistries and

  20. The pH ruler: a Java applet for developing interactive exercises on acids and bases.

    PubMed

    Barrette-Ng, Isabelle H

    2011-07-01

    In introductory biochemistry courses, it is often a struggle to teach the basic concepts of acid-base chemistry in a manner that is relevant to biological systems. To help students gain a more intuitive and visual understanding of abstract acid-base concepts, a simple graphical construct called the pH ruler Java applet was developed. The applet allows students to visualize the abundance of different protonation states of diprotic and triprotic amino acids at different pH values. Using the applet, the student can drag a widget on a slider bar to change the pH and observe in real time changes in the abundance of different ionization states of this amino acid. This tool provides a means for developing more complex inquiry-based, active-learning exercises to teach more advanced topics of biochemistry, such as protein purification, protein structure and enzyme mechanism.

  1. A Study on Advanced Lithium-Based Battery Cell Chemistries to Enhance Lunar Exploration Missions

    NASA Technical Reports Server (NTRS)

    Reid, Concha M.; Bennett, William R.

    2010-01-01

    NASAs Exploration Technology Development Program (ETDP) Energy Storage Project conducted an advanced lithium-based battery chemistry feasibility study to determine the best advanced chemistry to develop for the Altair Lunar Lander and the Extravehicular Activities (EVA) advanced Lunar surface spacesuit. These customers require safe, reliable batteries with extremely high specific energy as compared to state-of-the-art. The specific energy goals for the development project are 220 watt-hours per kilogram (Wh/kg) delivered at the battery-level at 0 degrees Celsius ( C) at a C/10 discharge rate. Continuous discharge rates between C/5 and C/2, operation between 0 and 30 C and 200 cycles are targeted. Electrode materials that were considered include layered metal oxides, spinel oxides, and olivine-type cathode materials, and lithium metal, lithium alloy, and silicon-based composite anode materials. Advanced cell chemistry options were evaluated with respect to multiple quantitative and qualitative attributes while considering their projected performance at the end of the available development timeframe. Following a rigorous ranking process, a chemistry that combines a lithiated nickel manganese cobalt oxide Li(LiNMC)O2 cathode with a silicon-based composite anode was selected as the technology that can potentially offer the best combination of safety, specific energy, energy density, and likelihood of success.

  2. Configurations of base-pair complexes in solutions. [nucleotide chemistry

    NASA Technical Reports Server (NTRS)

    Egan, J. T.; Nir, S.; Rein, R.; Macelroy, R.

    1978-01-01

    A theoretical search for the most stable conformations (i.e., stacked or hydrogen bonded) of the base pairs A-U and G-C in water, CCl4, and CHCl3 solutions is presented. The calculations of free energies indicate a significant role of the solvent in determining the conformations of the base-pair complexes. The application of the continuum method yields preferred conformations in good agreement with experiment. Results of the calculations with this method emphasize the importance of both the electrostatic interactions between the two bases in a complex, and the dipolar interaction of the complex with the entire medium. In calculations with the solvation shell method, the last term, i.e., dipolar interaction of the complex with the entire medium, was added. With this modification the prediction of the solvation shell model agrees both with the continuum model and with experiment, i.e., in water the stacked conformation of the bases is preferred.

  3. The Acid Catalyzed Nitration of Methanol: Formation of Methyl Nitrate via Aerosol Chemistry

    NASA Technical Reports Server (NTRS)

    Riffel, Brent G.; Michelsen, Rebecca R.; Iraci, Laura T.

    2004-01-01

    The liquid phase acid catalyzed reaction of methanol with nitric acid to yield methyl nitrate under atmospheric conditions has been investigated using gas phase infrared spectroscopy. This nitration reaction is expected to occur in acidic aerosol particles found in the upper troposphere/lower stratosphere as highly soluble methanol and nitric acid diffuse into these aerosols. Gaseous methyl nitrate is released upon formation, suggesting that some fraction of NO(x) may he liberated from nitric acid (methyl nitrate is later photolyzed to NO(x)) before it is removed from the atmosphere by wet deposition. Thus, this reaction may have important implications for the NO(x) budget. Reactions have been initiated in 45-62 wt% H2SO4 solutions at 10.0 C. Methyl nitrate production rates increased exponentially with acidity within the acidity regime studied. Preliminary calculations suggest that the nitronium ion (NO2(+) is the active nitrating agent under these conditions. The reaction order in methanol appears to depend on the water/methanol ratio and varies from first to zeroth order under conditions investigated. The nitration is first order in nitronium at all acidities investigated. A second order rate constant, kappa(sub 2), has been calculated to be 1 x 10(exp 8)/ M s when the reaction is first order in methanol. Calculations suggest the nitration is first order in methanol under tropospheric conditions. The infinitesimal percentage of nitric acid in the nitronium ion form in this acidity regime probably makes this reaction insignificant for the upper troposphere; however, this nitration may become significant in the mid stratosphere where colder temperatures increase nitric acid solubility and higher sulfuric acid content shifts nitric acid speciation toward the nitronium ion.

  4. Mannich bases in medicinal chemistry and drug design.

    PubMed

    Roman, Gheorghe

    2015-01-07

    The biological activity of Mannich bases, a structurally heterogeneous class of chemical compounds that are generated from various substrates through the introduction of an aminomethyl function by means of the Mannich reaction, is surveyed, with emphasis on the relationship between structure and biological activity. The review covers extensively the literature reports that have disclosed Mannich bases as anticancer and cytotoxic agents, or compounds with potential antibacterial and antifungal activity in the last decade. The most relevant studies on the activity of Mannich bases as antimycobacterial agents, antimalarials, or antiviral candidates have been included as well. The review contains also a thorough coverage of anticonvulsant, anti-inflammatory, analgesic and antioxidant activities of Mannich bases. In addition, several minor biological activities of Mannich bases, such as their ability to regulate blood pressure or inhibit platelet aggregation, their antiparasitic and anti-ulcer effects, as well as their use as agents for the treatment of mental disorders have been presented. The review gives in the end a brief overview of the potential of Mannich bases as inhibitors of various enzymes or ligands for several receptors.

  5. 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).

  6. Elucidation of noble metal/formic acid chemistry during DWPF feed preparation. Revision 1

    SciTech Connect

    Landon, L.F.

    1991-12-31

    Eleven reports are included: evaluation of noble metal compounds as catalysts for aerobic decomposition of formic acid; reaction of NaNO{sub 3} and NaNO{sub 2} with formic acid under argon; effects of Ru, Rh, Pd chlorides on formic acid decomposition in presence of IDMS (pH=11.0) sludge; effects of additives on catalysts on decomposition of formic acid to hydrogen; Rh-catalyzed decomposition of formic acid; the question of whether this decomposition can be heterogeneous catalysis; inhibition of this reaction by additives; nitrilotriacetic acid inhibitor; uses of gelatin and other water soluble polymers to control flocculation rate; comparison of catalytic activities of Rh, Ru, Pd in Purex and HM sludges; experiments on homogeneous vs heterogeneous nature of Rh catalyst. Figs, refs, tabs.

  7. Elucidation of noble metal/formic acid chemistry during DWPF feed preparation

    SciTech Connect

    Landon, L.F.

    1991-01-01

    Eleven reports are included: evaluation of noble metal compounds as catalysts for aerobic decomposition of formic acid; reaction of NaNO[sub 3] and NaNO[sub 2] with formic acid under argon; effects of Ru, Rh, Pd chlorides on formic acid decomposition in presence of IDMS (pH=11.0) sludge; effects of additives on catalysts on decomposition of formic acid to hydrogen; Rh-catalyzed decomposition of formic acid; the question of whether this decomposition can be heterogeneous catalysis; inhibition of this reaction by additives; nitrilotriacetic acid inhibitor; uses of gelatin and other water soluble polymers to control flocculation rate; comparison of catalytic activities of Rh, Ru, Pd in Purex and HM sludges; experiments on homogeneous vs heterogeneous nature of Rh catalyst. Figs, refs, tabs.

  8. D-erythroascorbic acid: Its preparations, chemistry, and metabolism (fungi and plants)

    SciTech Connect

    Loewus, F.A. . Inst. of Biological Chemistry); Seib, P.A. . Dept. of Grain Science and Industry)

    1990-01-01

    Sclerotinia sclerotiorum contains D-erythroascorbic acid (EAA) and a closely related reducing acid, possibly the open-chain form of EAA. The organism cleaves one of these products or possibly both to yield OA and D-glyceric acid. The OA is rapidly secreted into the medium. An analogy can be made between AA-linked OA biosynthesis in higher plants and EAA-linked OA biosynthesis in fungi as exemplified by S. sclerotiorum.

  9. Schiff bases: a short survey on an evergreen chemistry tool.

    PubMed

    Qin, Wenling; Long, Sha; Panunzio, Mauro; Biondi, Stefano

    2013-10-08

    The review reports a short biography of the Italian naturalized chemist Hugo Schiff and an outline on the synthesis and use of his most popular discovery: the imines, very well known and popular as Schiff Bases. Recent developments on their "metallo-imines" variants have been described. The applications of Schiff bases in organic synthesis as partner in Staudinger and hetero Diels-Alder reactions, as "privileged" ligands in the organometallic complexes and as biological active Schiff intermediates/targets have been reported as well.

  10. [Practical chemistry education provided by team-based learning (TBL) and peer evaluation].

    PubMed

    Yasuhara, Tomohisa; Konishi, Motomi; Nishida, Takahiro; Kushihata, Taro; Sone, Tomomichi; Kurio, Wasako; Yamamoto, Yumi; Nishikawa, Tomoe; Yanada, Kazuo; Nakamura, Mitsutaka

    2014-01-01

    Learning chemistry is cumulative: basic knowledge and chemical calculation skills are required to gain understanding of higher content. However, we often suffer from students' lack of learning skills to acquire these concepts. One of the reasons is the lack of adequate training in the knowledge and skills of chemistry, and one of the reasons for this lack is the lack of adequate evaluation of training procedures and content. Team-based learning (TBL) is a strong method for providing training in the knowledge and skills of chemistry and reaffirms the knowledge and skills of students of various levels. In our faculty, TBL exercises are provided for first-year students concurrently with lectures in physical chemistry and analytical chemistry. In this study, we researched the adoption of a peer evaluation process for this participatory learning model. Questionnaires taken after TBL exercises in the previous year showed a positive response to TBL. Further, a questionnaire taken after TBL exercises in the spring semester of the current year also yielded a positive response not only to TBL but also to peer evaluation. In addition, a significant correlation was observed between the improvement of students' grades in chemistry classes and the feeling the percentage (20%) of peer evaluation in overall evaluation low (logistic regression analysis, p=0.022). On the basis of the findings, we argue that TBL provides a generic, practical learning environment including an effective focus on learning strategy and evaluation of knowledge, skills, and attitudes, and studies on the educational effects of TBL and peer evaluation.

  11. A Computer Based Problem Solving Environment in Chemistry

    ERIC Educational Resources Information Center

    Bilgin, Ibrahim; Karakirik, Erol

    2005-01-01

    The purpose of this study was to introduce the Mole Solver, a computer based system that facilitates monitors and improves the students' problems solving skills on mole concept. The system has three distinct modes that: i) finds step by step solutions to the word problems on the mole concept ii) enable students' to solve word problems on their own…

  12. A Computer Based Problem Solving Environment in Chemistry

    ERIC Educational Resources Information Center

    Bilgin, Ibrahim; Karakirik, Erol

    2005-01-01

    The purpose of this study was to introduce the Mole Solver, a computer based system that facilitates monitors and improves students' problem solving skills on mole concept. The system has three distinct modes that: (1) find step by step solutions to the word problems on the mole concept; (2) enable students to solve word problems on their own by…

  13. Interfacial chemistry and the design of solid-phase nucleic acid hybridization assays using immobilized quantum dots as donors in fluorescence resonance energy transfer.

    PubMed

    Algar, W Russ; Krull, Ulrich J

    2011-01-01

    The use of quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) offer several advantages for the development of multiplexed solid-phase QD-FRET nucleic acid hybridization assays. Designs for multiplexing have been demonstrated, but important challenges remain in the optimization of these systems. In this work, we identify several strategies based on the design of interfacial chemistry for improving sensitivity, obtaining lower limits of detection (LOD) and enabling the regeneration and reuse of solid-phase QD-FRET hybridization assays. FRET-sensitized emission from acceptor dyes associated with hybridization events at immobilized QD donors provides the analytical signal in these assays. The minimization of active sensing area reduces background from QD donor PL and allows the resolution of smaller amounts of acceptor emission, thus lowering the LOD. The association of multiple acceptor dyes with each hybridization event can enhance FRET efficiency, thereby improving sensitivity. Many previous studies have used interfacial protein layers to generate selectivity; however, transient destabilization of these layers is shown to prevent efficient regeneration. To this end, we report a protein-free interfacial chemistry and demonstrate the specific detection of as little as 2 pmol of target, as well as an improved capacity for regeneration.

  14. Linear Titration Curves of Acids and Bases.

    PubMed

    Joseph, N R

    1959-05-29

    The Henderson-Hasselbalch equation, by a simple transformation, becomes pH - pK = pA - pB, where pA and pB are the negative logarithms of acid and base concentrations. Sigmoid titration curves then reduce to straight lines; titration curves of polyelectrolytes, to families of straight lines. The method is applied to the titration of the dipeptide glycyl aminotricarballylic acid, with four titrable groups. Results are expressed as Cartesian and d'Ocagne nomograms. The latter is of a general form applicable to polyelectrolytes of any degree of complexity.

  15. Hydrologic landscapes on the Delmarva Peninsula Part 1: Drainage basin type and base-flow chemistry

    USGS Publications Warehouse

    Phillips, P.J.; Bachman, L.J.

    1996-01-01

    The relation between landscape characteristics and water chemistry on the Delmarva Peninsula can be determined through a principal-component analysis of basin characteristics. Two basin types were defined by factor scores: (1) well-drained basins, characterized by combinations of a low percentage of forest cover, a low percentage of poorly drained soil, and elevated channel slope; and (2) poorly drained basins, characterized by a combinations of an elevated percentage of forest cover, an elevated percentage of poorly drained soil, and low channel slopes. Results from base- flow sampling of 29 basins during spring 1991 indicate that water chemistry of the two basin types differ significantly. Concentrations of calcium, magnesium, potassium, alkalinity, chloride, and nitrate are elevated in well- drained basins, and specific conductance is elevated. Concentrations of aluminum, dissolved organic carbon, sodium, and silica are elevated in poorly drained basins whereas specific conductance is low. The chemical patterns found in well-drained basins can be attributed to the application of agricultural chemicals, and those in poorly drained basins can be attributed to ground-water flowpaths. These results indicate that basin types determined by a quantitative analysis of basin characteristics can be related statistically to differences in base-flow chemistry, and that the observed statistical differences can be related to major processes that affect water chemistry.

  16. Stream chemistry in the eastern United States. 2. Current sources of acidity in acidic and low acid-neutralizing-capacity streams

    SciTech Connect

    Herlihy, A.T.; Kaufmann, P.R.; Mitch, M.E.

    1991-01-01

    The authors examined anion composition in National Stream Survey (NSS) data in order to evaluate the most probable sources of current acidity in acidic and low acid neutralizing capacity (ANC) streams in the eastern United States. Acidic streams that had almost no organic influence (less than 10% of total anions) and sulfate and nitrate concentrations indicative of evaporative concentration of atmospheric deposition were classified as acidic due to acidic deposition. These acidic streams were located in small forested watersheds in the Mid-Atlantic Highlands (an estimated 1950 km of stream length) and in the Mid-Atlantic Coastal Plain (1250 km). Acidic streams affected primarily by acidic deposition but also influenced by naturally occurring organic anions accounted for another 1180 km of acidic stream length and were located in the New Jersey Pine Barrens, plateau tops in the Mid-Atlantic and Southeast Highlands, and the Florida Panhandle. The total length of streams acidic due to acid mine drainage in the NSS (4590 km) was about the same as the total length of acidic streams likely affected by acidic deposition (4380 km). Acidic streams whose acid anion composition was dominated by organics were located in Florida and the Mid-Atlantic Coastal Plain. In Florida, most of the acidic streams were organic dominated, whereas about half of the streams in the Mid-Atlantic Coastal Plain were organic dominated. Organic-dominated acidic streams were not observed in the Mid-Atlantic and Southeast Highlands.

  17. Stream chemistry in the eastern United States, 2, Current sources of acidity in acidic and low acid-neutralizing capacity streams

    NASA Astrophysics Data System (ADS)

    Herlihy, Alan T.; Kaufmann, Philip R.; Mitch, Mark E.

    1991-04-01

    We examined anion composition in National Stream Survey (NSS) data in order to evaluate the most probable sources of current acidity in acidic and low acid-neutralizing capacity (ANC) streams in the eastern United States. Acidic streams that had almost no organic influence (less than 10% of total anions) and sulfate and nitrate concentrations indicative of evaporative concentration of atmospheric deposition were classified as acidic due to acidic deposition. These acidic streams were located in small (<30 km2) forested watersheds in the Mid-Atlantic Highlands (an estimated 1950 km of stream length) and in the Mid-Atlantic Coastal Plain (1250 km). Acidic streams affected primarily by acidic deposition but also influenced by naturally occurring organic anions accounted for another 1180 km of acidic stream length and were located in the New Jersey Pine Barrens, plateau tops in the Mid-Atlantic and Southeast Highlands, and the Florida Panhandle. The total length of streams acidic due to acid mine drainage in the NSS (4590 km) was about the same as the total length of acidic streams likely affected by acidic deposition (4380 km). Acidic streams whose acid anion composition was dominated by organics were located in Florida and the Mid-Atlantic Coastal Plain. In Florida, most of the acidic streams were organic dominated, whereas about half of the streams in the Mid-Atlantic Coastal Plain were organic dominated. Organic-dominated acidic streams were not observed in the Mid-Atlantic and Southeast Highlands.

  18. Analysis of survey data on the chemistry of twenty-three streams in the Chesapeake Bay watershed: some implications of the impact of acid deposition. Final report

    SciTech Connect

    Janicki, A.; Cummins, R.

    1983-12-01

    A survey of the chemistry of 23 streams within the Chesapeake Bay watershed was conducted in the spring of 1983 to determine whether a potential for changes in water chemistry due to atmospheric inputs of acidic materials exists in any of these streams. Sampling was conducted weekly through the months of March and April. Three streams were identified as being likely affected by acid inputs due to relatively high H(+) and SO4(-2) concentrations and low alkalinities: Stockett's Run, Lyons Creek, and Muddy Creek. Elevated dissolved aluminum concentrations were observed in some Eastern Shore streams and are likely related to the predominance of clay soils in their watersheds.

  19. Coordination chemistry of N-heterocyclic nitrenium-based ligands.

    PubMed

    Tulchinsky, Yuri; Kozuch, Sebastian; Saha, Prasenjit; Mauda, Assaf; Nisnevich, Gennady; Botoshansky, Mark; Shimon, Linda J W; Gandelman, Mark

    2015-05-04

    Comprehensive studies on the coordination properties of tridentate nitrenium-based ligands are presented. N-heterocyclic nitrenium ions demonstrate general and versatile binding abilities to various transition metals, as exemplified by the synthesis and characterization of Rh(I) , Rh(III) , Mo(0) , Ru(0) , Ru(II) , Pd(II) , Pt(II) , Pt(IV) , and Ag(I) complexes based on these unusual ligands. Formation of nitrenium-metal bonds is unambiguously confirmed both in solution by selective (15) N-labeling experiments and in the solid state by X-ray crystallography. The generality of N-heterocyclic nitrenium as a ligand is also validated by a systematic DFT study of its affinity towards all second-row transition and post-transition metals (Y-Cd) in terms of the corresponding bond-dissociation energies.

  20. Patent Retrieval in Chemistry based on Semantically Tagged Named Entities

    DTIC Science & Technology

    2009-11-01

    their corresponding synonyms. An ex- ample query for TS-15 is: (" Betaine " OR "Glycine betaine " OR "Glycocol betaine " OR "Glycylbetaine" OR ...) AND...task in an automatic way based on noun- phrase detection incorporating the OpenNLP chun- 3 Informative Term Synonyms Source Betaine Glycine betaine ...Glycocol betaine , Glycylbetaine etc. ATC Peripheral Artery Disease Peripheral Artery Disorder, Peripheral Arterial Disease etc. MeSH Diels-Alder reaction

  1. Aromatic Amino Acids and Related Substances: Chemistry, Biology, Medicine, and Application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    On the occasion of the "Transdisciplinary International Conference on Aromatic Amino Acids and Related Substances," the organizing committee honors and thanks the expert participants from many areas of aromatic amino acid (AAA)3 research. In this transdisciplinary meeting, "aromatic paradigms" were ...

  2. Ingested boric acid effect on the venom chemistry of Solenopsis invicta Buren (Hymenoptera: Formicidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    During a field evaluation of a boric acid bait against the red imported fire ant, Solenopsis invicta Buren, it was observed that workers of intoxicated colonies produced stings with less toxic effects compared to workers from healthy colonies. In this study, the effect of boric acid on the levels o...

  3. Theoretical Hammett Plot for the Gas-Phase Ionization of Benzoic Acid versus Phenol: A Computational Chemistry Lab Exercise

    ERIC Educational Resources Information Center

    Ziegler, Blake E.

    2013-01-01

    Computational chemistry undergraduate laboratory courses are now part of the chemistry curriculum at many universities. However, there remains a lack of computational chemistry exercises available to instructors. This exercise is presented for students to develop skills using computational chemistry software while supplementing their knowledge of…

  4. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1978

    1978-01-01

    Describes some laboratory apparatus, chemistry experiments and demonstrations, such as a Kofler block melting point apparatus, chromatographic investigation of the phosphoric acid, x-ray diffraction, the fountain experiment, endothermic sherbet, the measurement of viscosity, ionization energies and electronic configurations. (GA)

  5. A Quantitative Assessment of a Medicinal Chemistry Problem-based Learning Sequence

    PubMed Central

    Webster, Andrew A.; Riggs, Robert M.

    2006-01-01

    Objectives To establish an aggressive problem-based learning (PBL) format for the medicinal chemistry course and assess the outcomes of student learning. Methods To assess learning in the new format, precourse and postcourse examinations were given to students enrolled before and after problem-based learning was implemented, and appropriate statistical analyses were conducted. Results The PBL cohort did not learn the same amount of factual content yet performed the same on higher-order thought questions as the non-PBL cohort. Conclusions Problem-based learning may not be the ideal method for teaching medicinal chemistry. This may be due to several factors including: student learning type, the lack of a cognitive framework for learning in the basic sciences, and time constraints. PMID:17136208

  6. Academic Success in Context-Based Chemistry: Demonstrating fluid transitions between concepts and context

    NASA Astrophysics Data System (ADS)

    King, Donna Therese; Ritchie, Stephen M.

    2013-05-01

    Curriculum developers and researchers have promoted context-based programmes to arrest waning student interest and participation in the enabling sciences at high school and university. Context-based programmes aim for student connections between scientific discourse and real-world contexts to elevate curricular relevance without diminishing conceptual understanding. This interpretive study explored the learning transactions in one 11th grade context-based chemistry classroom where the context was the local creek. The dialectic of agency/structure was used as a lens to examine how the practices in classroom interactions afforded students the agency for learning. The results suggest that first, fluid transitions were evident in the student-student interactions involving successful students; and second, fluid transitions linking concepts to context were evident in the students' successful reports. The study reveals that the structures of writing and collaborating in groups enabled students' agential and fluent movement between the field of the real-world creek and the field of the formal chemistry classroom. Furthermore, characteristics of academically successful students in context-based chemistry are highlighted. Research, teaching, and future directions for context-based science teaching are discussed.

  7. 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.

  8. The impact of ice uptake of nitric acid on atmospheric chemistry

    NASA Astrophysics Data System (ADS)

    von Kuhlmann, R.; Lawrence, M. G.

    2006-01-01

    The potential impact of the uptake of HNO3 on ice on the distribution of NOy species, ozone and OH has been assessed using the global scale chemistry-transport model MATCH-MPIC. Assuming equilibrium uptake according to dissociative Langmuir theory results in significant reductions of gas phase HNO3. Comparison to a large set of observations provides support that significant uptake of HNO3 on ice is occurring, but the degree of the uptake cannot be inferred from this comparison alone. Sensitivity simulations show that the uncertainties in the total amount of ice formation in the atmosphere and the actual expression of the settling velocity of ice particles only result in small changes in our results. The largest uncertainty is likely to be linked to the actual theory describing the uptake process and the value of the initial uptake coefficient. The inclusion of non-methane hydrocarbon chemistry partially compensates for the absence of HNO3 uptake on ice when this is neglected in the model. The calculated overall effect on upper tropospheric ozone concentrations and the tropospheric methane lifetime are moderate to low. These results support a shift in the motivation for future experimental and theoretical studies of HNO3-ice interaction towards the role of HNO3 in hydrometeor surface physics.

  9. The impact of ice uptake of nitric acid on atmospheric chemistry

    NASA Astrophysics Data System (ADS)

    von Kuhlmann, R.; Lawrence, M. G.

    2005-08-01

    The potential impact of the uptake of HNO3 on ice on the distribution of NOy species, ozone and OH has been assessed using the global scale chemistry-transport model MATCH-MPIC. Assuming equilibrium uptake according to dissociative Langmuir theory results in significant reductions of gas phase HNO3. Comparison to a large set of observations provides support that significant uptake of HNO3 on ice is occurring, but the degree of the uptake cannot be inferred from this comparison alone. Sensitivity simulations show that the uncertainties in the total amount of ice formation in the atmosphere and the actual expression of the settling velocity of ice particles only result in small changes in our results. The largest uncertainty is likely to be linked to the actual theory describing the uptake process. The inclusion of non-methane hydrocarbon chemistry buffers the overall effect of neglected uptake of HNO3 on ice. The calculated overall effect on upper tropospheric ozone concentrations and the tropospheric methane lifetime are moderate to low. These results support a shift in the motivation for future experimental and theoretical studies of HNO3-ice interaction towards the role of HNO3 in hydrometeor surface physics.

  10. The chemistry of lava-seawater interactions: The generation of acidity

    SciTech Connect

    Resing, J.A.; Sansone, F.J.

    1999-08-01

    High concentrations of acid were found to arise from the interaction between molten rock and seawater at the shoreline of Kilauea Volcano, Hawaii. A series of field samplings and experiments show that the acid was derived from two sources: the release of magmatic volatiles and water-rock reactions. Although the bulk of the magmatic volatiles (CO{sub 2}, H{sub 2}O, and SO{sub 2}) are vented at Puu Oo cinder cone before the lava`s transit downslope to the ocean, a portion of the sulfur (S) and fluoride (F) gases are retained by the lava and then are released partially when the lava is quenched by seawater. The primary water-rock reaction responsible for acid formation appears to be Na-metasomatism, which is much different from the predominant acid-forming reaction found in submarine hydrothermal systems, Mg-metasomatism. Analyses of surface seawater and of precipitation (rain) deposited at the shore show that {approximately}30% of the acid comes from magmatic gases with the balance from reactions between the rock and the salts found in seawater. Experimental results show that {approximately}4 {+-} 1.5 mEq of acid are formed per kilogram of lava entering the ocean, and of this 1 {+-} 0.5 mEq/kg of lava came from S and F, with the balance coming from water-rock reactions. On the basis of lava extrusion rates, {approximately}200--720 {times} 10{sup 6} Eq/yr of acid are being formed at this site. The deposition of the acid results in the alteration of subaerial lava flows along the coast, and the lowering of the pH of the adjacent surface ocean waters by more than 1 unit. The ejection of this acid into the atmosphere contributes to the formation of an extensive haze downwind of the lava entries.

  11. Experimental and computational investigation of acetic acid deoxygenation over oxophilic molybdenum carbide: Surface chemistry and active site identity

    SciTech Connect

    Schaidle, Joshua A.; Blackburn, Jeffrey; Farberow, Carrie A.; Nash, Connor; Steirer, K. Xerxes; Clark, Jared; Robichaud, David J.; Ruddy, Daniel A.

    2016-01-21

    Ex situ catalytic fast pyrolysis (CFP) is a promising route for producing fungible biofuels; however, this process requires bifunctional catalysts that favor C–O bond cleavage, activate hydrogen at near atmospheric pressure and high temperature (350–500 °C), and are stable under high-steam, low hydrogen-to-carbon environments. Recently, early transition-metal carbides have been reported to selectively cleave C–O bonds of alcohols, aldehydes, and oxygenated aromatics, yet there is limited understanding of the metal carbide surface chemistry under reaction conditions and the identity of the active sites for deoxygenation. In this study, we evaluated molybdenum carbide (Mo2C) for the deoxygenation of acetic acid, an abundant component of biomass pyrolysis vapors, under ex situ CFP conditions, and we probed the Mo2C surface chemistry, identity of the active sites, and deoxygenation pathways using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations.

  12. Experimental and computational investigation of acetic acid deoxygenation over oxophilic molybdenum carbide: Surface chemistry and active site identity

    DOE PAGES

    Schaidle, Joshua A.; Blackburn, Jeffrey; Farberow, Carrie A.; ...

    2016-01-21

    Ex situ catalytic fast pyrolysis (CFP) is a promising route for producing fungible biofuels; however, this process requires bifunctional catalysts that favor C–O bond cleavage, activate hydrogen at near atmospheric pressure and high temperature (350–500 °C), and are stable under high-steam, low hydrogen-to-carbon environments. Recently, early transition-metal carbides have been reported to selectively cleave C–O bonds of alcohols, aldehydes, and oxygenated aromatics, yet there is limited understanding of the metal carbide surface chemistry under reaction conditions and the identity of the active sites for deoxygenation. In this study, we evaluated molybdenum carbide (Mo2C) for the deoxygenation of acetic acid, anmore » abundant component of biomass pyrolysis vapors, under ex situ CFP conditions, and we probed the Mo2C surface chemistry, identity of the active sites, and deoxygenation pathways using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations.« less

  13. Coagulation removal of humic acid-stabilized carbon nanotubes from water by PACl: influences of hydraulic condition and water chemistry.

    PubMed

    Ma, Si; Liu, Changli; Yang, Kun; Lin, Daohui

    2012-11-15

    Discharged carbon nanotubes (CNTs) can adsorb the widely-distributed humic acid (HA) in aquatic environments and thus be stabilized. HA-stabilized CNTs can find their way into and challenge the potable water treatment system. This study investigated the efficiency of coagulation and sedimentation techniques in the removal of the HA-stabilized multi-walled carbon nanotubes (MWCNTs) using polyaluminum chloride (PACl) as a coagulant, with a focus on the effects of hydraulic conditions and water chemistry. Stirring speeds in the mixing and reacting stages were gradually changed to examine the effect of the hydraulic conditions on the removal rate. The stirring speed in the reacting stage affected floc formation and thereby had a greater impact on the removal rate than the stirring speed in the mixing stage. Water chemistry factors such as pH and ionic strength had a significant effect on the stability of MWCNT suspension and the removal efficiency. Low pH (4-7) was favorable for saving the coagulant and maintaining high removal efficiency. High ionic strength facilitated the destabilization of the HA-stabilized MWCNTs and thereby lowered the required PACl dosage for the coagulation. However, excessively high ionic strength (higher than the critical coagulation concentration) decreased the maximum removal rate, probably by inhibiting ionic activity of PACl hydrolyzate in water. These results are expected to shed light on the potential improvement of coagulation removal of aqueous stabilized MWCNTs in water treatment systems.

  14. Textbook Questions in Context-Based and Traditional Chemistry Curricula Analysed from a Content Perspective and a Learning Activities Perspective

    ERIC Educational Resources Information Center

    Overman, Michelle; Vermunt, Jan D.; Meijer, Paulien C.; Bulte, Astrid M. W.; Brekelmans, Mieke

    2013-01-01

    In this study, questions in context-based and traditional chemistry textbooks were analysed from two perspectives that are at the heart of chemistry curricula reforms: a content perspective and a learning activities perspective. To analyse these textbook questions, we developed an instrument for each perspective. In total, 971 textbook questions…

  15. The Efficacy of Problem-Based Learning in an Analytical Laboratory Course for Pre-Service Chemistry Teachers

    ERIC Educational Resources Information Center

    Yoon, Heojeong; Woo, Ae Ja; Treagust, David; Chandrasegaran, A. L.

    2014-01-01

    The efficacy of problem-based learning (PBL) in an analytical chemistry laboratory course was studied using a programme that was designed and implemented with 20 students in a treatment group over 10 weeks. Data from 26 students in a traditional analytical chemistry laboratory course were used for comparison. Differences in the creative thinking…

  16. Development and Preliminary Impacts of the Implementation of an Authentic Research-Based Experiment in General Chemistry

    ERIC Educational Resources Information Center

    Tomasik, Janice Hall; Cottone, Katelyn E.; Heethuis, Mitchell T.; Mueller, Anja

    2013-01-01

    Incorporating research-based lab activities into general chemistry at a large university can be challenging, considering the high enrollments and costs typically associated with the courses. Performing sweeping curricular overhauls of the general chemistry laboratory can be difficult, and in some cases discouraged, as many would rather maintain…

  17. Teaching Techniques in Clinical Chemistry.

    ERIC Educational Resources Information Center

    Wilson, Diane

    This master's thesis presents several instructional methods and techniques developed for each of eleven topics or subject areas in clinical chemistry: carbohydrate metabolism, lipid metabolism, diagnostic enzymology, endocrinology, toxicology, quality control, electrolytes, acid base balance, hepatic function, nonprotein nitrogenous compounds, and…

  18. Visualizing Chemistry: Investigations for Teachers.

    ERIC Educational Resources Information Center

    Ealy, Julie B.; Ealy, James L., Jr.

    This book contains 101 investigations for chemistry classrooms. Topics include: (1) Physical Properties; (2) Reactions of Some Elements; (3) Reactions Involving Gases; (4) Energy Changes; (5) Solutions and Solubility; (6) Transition Metals and Complex Ions; (7) Kinetics and Equilibrium; (8) Acids and Bases; (9) Oxidation-Reduction; (10)…

  19. Recovery Processes of Organic Acids from Fermentation Broths in the Biomass-Based Industry.

    PubMed

    Li, Qian-Zhu; Jiang, Xing-Lin; Feng, Xin-Jun; Wang, Ji-Ming; Sun, Chao; Zhang, Hai-Bo; Xian, Mo; Liu, Hui-Zhou

    2016-01-01

    The new movement towards green chemistry and renewable feedstocks makes microbial production of chemicals more competitive. Among the numerous chemicals, organic acids are more attractive targets for process development efforts in the renewable-based biorefinery industry. However, most of the production costs in microbial processes are higher than that in chemical processes, among which over 60% are generated by separation processes. Therefore, the research of separation and purification processes is important for a promising biorefinery industry. This review highlights the progress of recovery processes in the separation and purification of organic acids, including their advantages and disadvantages, current situation, and future prospects in terms of recovery yields and industrial application.

  20. Chirality as a tool in nucleic acid recognition: principles and relevance in biotechnology and in medicinal chemistry.

    PubMed

    Corradini, Roberto; Sforza, Stefano; Tedeschi, Tullia; Marchelli, Rosangela

    2007-05-05

    The understanding of the interaction of chiral species with DNA or RNA is very important for the development of new tools in biology and of new drugs. Several cases in which chirality is a crucial point in determining the DNA binding mode are reviewed and discussed, with the aim of illustrating how chirality can be considered as a tool for improving the understanding of mechanisms and the effectiveness of nucleic acid recognition. The review is divided into two parts: the former describes examples of chiral species interacting with DNA: intercalators, metal complexes, and groove binders; the latter part is dedicated to chirality in DNA analogs, with discussion of phosphate stereochemistry and chirality of ribose substitutes, in particular of peptide nucleic acids (PNAs) for which a number of works have been published recently dealing with the effect of chirality in DNA recognition. The discussion is intended to show how enantiomeric recognition originates at the molecular level, by exploiting the enormous progresses recently achieved in the field of structural characterization of complexes formed by nucleic acid with their ligands by crystallographic and spectroscopic methods. Examples of application of the DNA binding molecules described and the role of chirality in DNA recognition relevant for biotechnology or medicinal chemistry are reported.

  1. Development and Evaluation of Internet-Based Hypermedia Chemistry Tutorials

    NASA Astrophysics Data System (ADS)

    Tissue, Brian M.; Earp, Ronald L.; Yip, Ching-Wan; Anderson, Mark R.

    1996-05-01

    This progress report describes the development and student use of World-Wide-Web-based prelaboratory exercises in senior-level Instrumental Analysis during the 1995 Fall semester. The laboratory preparation exercises contained hypermedia tutorials and multiple-choice questions that were intended to familiarize the students with the experiments and instrumentation before their laboratory session. The overall goal of our work is to explore ways in which computer and network technology can be applied in education to improve the cost-effectiveness and efficacy of teaching. The course material can be accessed at http://www.chem.vt.edu/chem-ed/4114/Fall1995.html. The students were instructed to read their experimental procedure and to do the relevant laboratory preparation exercise. The individual tutorial documents were primarily text that provided basic theoretical and experimental descriptions of analytical and instrumental methods. The documents included hyperlinks to basic concepts, simple schematics, and color graphics of experimental set-ups or instrumentation. We chose the World-Wide Web (WWW) as the delivery platform for this project because of the ease of developing, distributing, and modifying hypermedia material in a client-server system. The disadvantage of the WWW is that network bandwidth limits the size and sophistication of the hypermedia material. To minimize internet transfer time, the individual documents were kept short and usually contained no more than 3 or 4 inline images. After reading the tutorial the students answered several multiple-choice questions. The figure shows one example of a multiple-choice question and the response page. Clicking on the "Submit answer" button calls a *.cgi file, which contains instructions in the PERL interpretive language, that generates the response page and saves the date, time, and student's answer to a file on the server. Usage and student perception of the on-line material was evaluated from server logs and

  2. Chemistry of OH in remote clouds and its role in the production of formic acid and peroxymonosulfate

    NASA Technical Reports Server (NTRS)

    Jacob, D. J.

    1986-01-01

    The chemistry of OH in nonprecipitating tropospheric clouds was studied using a coupled gas phase/aqueous phase chemical model. The simulation takes into account the radial dependence of the concentrations of short lived aqueous phase species, in particular, O3(aq) OH(aq). Formic acid is shown to be rapidly produced by the aqueous phase reaction between H2C(OH)2 and OH, but HCOO(-) and OH, but HCOO(-) is in turn rapidly oxidized by OH(aq). The HCOOH concentration in cloud is shown to be strongly dependent on the pH of the cloud water; clouds with pH greater than 5 are not efficient HCOOH sources. A novel mechanism is proposed for the oxidation of S(IV) by OH(aq), with the main product predicted to be peroxymonosulfate, HSO5(-). The latter could contribute significantly to total cloud water sulfur.

  3. Click Chemistry Route to the Synthesis of Unusual Amino Acids, Peptides, Triazole-Fused Heterocycles and Pseudodisaccharides.

    PubMed

    Chandrasekaran, Srinivasan; Ramapanicker, Ramesh

    2017-01-01

    Conjugation of different molecular species using copper(I)-catalyzed click reaction between azides and terminal alkynes is among the best available methods to prepare multifunctional compounds. The effectiveness of this method has provided wider acceptance to the concept of click chemistry, which is now widely employed to synthesize densely functionalized organic molecules. This article summarizes the contributions from our group in the development of new methods for the synthesis of functional molecules using copper(I)-catalyzed click reactions. We have developed very efficient methods for the synthesis of peptides and amino acids conjugated with carbohydrates, thymidine and ferrocene. We have also developed an efficient strategy to synthesize triazole-fused heterocycles from primary amines, amino alochols and diols. Finally, an interesting method for the synthesis of pseudodisaccharides linked through triazoles, starting from carbohydrate-derived donor-acceptor cyclopropanes is discussed.

  4. Crystal density predictions for nitramines based on quantum chemistry.

    PubMed

    Qiu, Ling; Xiao, Heming; Gong, Xuedong; Ju, Xuehai; Zhu, Weihua

    2007-03-06

    An efficient and convenient method for predicting the crystalline densities of energetic materials was established based on the quantum chemical computations. Density functional theory (DFT) with four different basis sets (6-31G(**), 6-311G(**), 6-31+G(**), and 6-311++G(**)) and various semiempirical molecular orbital (MO) methods have been employed to predict the molecular volumes and densities of a series of energetic nitramines including acyclic, monocyclic, and polycyclic/cage molecules. The relationships between the calculated values and experimental data were discussed in detail, and linear correlations were suggested and compared at different levels. The calculation shows that if the selected basis set is larger, it will expend more CPU (central processing unit) time, larger molecular volume and smaller density will be obtained. And the densities predicted by the semiempirical MO methods are all systematically larger than the experimental data. In comparison with other methods, B3LYP/6-31G(**) is most accurate and economical to predict the solid-state densities of energetic nitramines. This may be instructive to the molecular designing and screening novel HEDMs.

  5. Wet chemistry applications for low dimensional bismuth-based solids

    NASA Astrophysics Data System (ADS)

    Shen, Wei-Ning

    This dissertation investigates the relationship between nanoporous microstructures and transport properties. A liquid-phase metalorganic deposition (IMOD) method has been implemented to synthesize Bi films with nano-size pores. Typical nanoporous Bi film preparation involves a spin-coat of a solution of Bi 2-ethylhexanoate with glycerol into 2-methyl-1-propanol solvent on Si substrates followed by a pyrolysis under pure H2. MOD was also used in Bi-based films and patterns. Bi2Te 3 films were prepared by mixing Bi and Te 2-methoxyethoxides in 2-methoxyethanol. Composite films of Bi2Te3-Bi and Bi2Se 3-Bi were obtained by mixing in Bi2Te3 and Bi 2Se3 platelet powders during MOD spin-coating. Patterns of Bi and Bi2Te3 were accomplished by using MOD solutions and soft lithography methods. Nanoporous Bi films with porosity of 11--50% (thickness from 20 to 570 nm) were prepared. The nanoporous Bi films exhibited some preferred orientation, with the (003) aligned parallel to the substrate. A H2 plasma treatment was applied to the Bi film to reduce the residual carbon impurities coming from MOD precursors. The nanoporous structure of the Bi films consists of inter-connected nanoporous channels between polygonal Bi crystallites (˜36 nm). Phonon scattering was influenced more by nanopore size than by the number of pores. Calculations suggested that the phonon mean free path of nanoporous Bi films was limited to 7A and was nearly independent of temperature (100 to 300K). The thermal conductivity of nanoporous, Bi films at 300K was dramatically reduced, to 0.1 W/mK, from the 2.5 W/mK value for dense films. In contrast, the electrical conductivity of nanoporous Bi films was slightly reduced, to 800 S/cm, only a factor of 2 less than that of a dense film at 300K. The Seebeck coefficient of nanoporous; Bi films with porosity of 11--23% at 300K varied from -25 to -45 muV/K. In general, both electrical and thermal conductivities were reduced as the porosity increased, while the

  6. Stream chemistry in the eastern United States. 2. Current sources of acidity in acidic and low acid-neutralizing capacity streams

    SciTech Connect

    Herlihy, A.T.; Kaufmann, P.R.; Mitch, M.E. )

    1991-04-01

    The authors examined anion composition in National Stream Survey (NSS) data in order to evaluate the most probably sources of current acidity in acidic and low acid-neutralizing capacity (ANC) streams in the eastern US. Acidic streams that had almost no organic influence (less than 10% of total anions) and sulfate and nitrate concentrations indicative of evaporative concentration of atmospheric deposition were classified as acidic due to acidic deposition. These acidic streams were located in small (<30 km{sup 2}) forested watersheds in the Mid-Atlantic Highlands (an estimated 1,950 km of stream length) and in the Mid-Atlantic Coastal Plain (1,250 km). Acidic streams affected primarily by acidic deposition but also influenced by naturally occurring organic anions accounted for another 1,180 km of acidic stream length, and were located in the New Jersey Pine Barrens, plateau tops in the Mid-Atlantic and Southeast Highlands, and the Florida Panhandle. The total length of streams acidic due to acid mine drainage in the NSS (4,590 km) was about the same as the total length of acidic streams likely affected by acidic deposition (4,380 km). Acidic streams whose acid anion composition was dominated by organics were located in Florida and the Mid-Atlantic Coastal Plain. In Florida, most of the acidic streams were organic dominated, whereas about half of the streams in the Mid-Atlantic Coastal Plain were organic dominated. Organic-dominated acidic streams were not observed in the Mid-Atlantic and Southeast Highlands.

  7. Fluorescent detection of copper(II) based on DNA-templated click chemistry and graphene oxide.

    PubMed

    Zhou, Lifen; Shen, Qinpeng; Zhao, Peng; Xiang, Bingbing; Nie, Zhou; Huang, Yan; Yao, Shouzhuo

    2013-12-15

    A novel DNA-templated click chemistry strategy for homogenous fluorescent detection of Cu(2+) has been developed based on click ligation-dependent DNA structure switch and the selective quenching ability of graphene oxide (GO) nanosheet. The clickable duplex probe consists of two DNA strands with alkyne and azide group, respectively, and Cu(+)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction can chemically ligate these two strands. Toehold sequence displacement was consequently exploited to achieve DNA structure transformation bearing fluorescent tag FAM. Cu(2+)-induced chemical ligation caused the probe transfer to hybrid structure with single stranded DNA (ssDNA) tail, while only duplex structure was obtained without Cu(2+). This structural difference can be probed by GO-based fluorescence detection due to the preferential binding of GO to ssDNA. Under the optimum conditions, this sensor can sensitively and specifically detect Cu(2+) with a low detection limit of 58 nM and a linear range of 0.1-10 μM. This new strategy is highly sensitive and selective for Cu(2+) detection because of the great specificity of click chemistry and super-quenching ability of GO. Moreover, with the aid of high efficient DNA templated synthesis, the detection process requires only about half an hour which is much quicker than previous click-chemistry-based Cu(2+) sensors.

  8. Enantiomeric Resolution of [Plus or Minus] Mandelic Acid by (1R,2S)-(--)-Ephedrine: An Organic Chemistry Laboratory Experiment Illustrating Stereoisomerism

    ERIC Educational Resources Information Center

    Baar, Marsha R.; Cerrone-Szakal, Andrea L.

    2005-01-01

    The experiment involving enantiomeric resolution, as an illustration of chiral technology, is an excellent early organic chemistry lab experiment. The success of this enantiomeric resolution can be judged by melting point, demonstrated by [plus or minus]-mandelic acid-(1R,2S)-(--)-ephedrine system.

  9. Is There a Need to Discuss Atomic Orbital Overlap When Teaching Hydrogen-Halide Bond Strength and Acidity Trends in Organic Chemistry?

    ERIC Educational Resources Information Center

    Devarajan, Deepa; Gustafson, Samantha J.; Bickelhaupt, F. Matthias; Ess, Daniel H.

    2015-01-01

    Undergraduate organic chemistry textbooks and Internet websites use a variety of approaches for presenting and explaining the impact of halogen atom size on trends in bond strengths and/or acidity of hydrogen halides. In particular, several textbooks and Internet websites explain these trends by invoking decreasing orbital overlap between the…

  10. Ion Exchange and Thin Layer Chromatographic Separation and Identification of Amino Acids in a Mixture: An Experiment for General Chemistry and Biotechnology Laboratories

    ERIC Educational Resources Information Center

    Brunauer, Linda S.; Caslavka, Katelyn E.; Van Groningen, Karinne

    2014-01-01

    A multiday laboratory exercise is described that is suitable for first-year undergraduate chemistry, biochemistry, or biotechnology students. Students gain experience in performing chromatographic separations of biomolecules, in both a column and thin layer chromatography (TLC) format. Students chromatographically separate amino acids (AA) in an…

  11. Chemistry in the Venus clouds: Sulfuric acid reactions and freezing behavior of aqueous liquid droplets

    NASA Astrophysics Data System (ADS)

    Delitsky, M. L.; Baines, K. H.

    2015-11-01

    Venus has a thick cloud deck at 40-70 km altitude consisting of liquid droplets and solid particles surrounded by atmospheric gases. The liquid droplets are highly concentrated aqueous solutions of sulfuric acid ranging in concentration from 70-99 wt%. Weight percent drops off with altitude (Imamura and Hashimoto 2001). There will be uptake of atmospheric gases into the droplet solutions and the ratios of gas-phase to liquid-phase species will depend on the Henry’s Law constant for those solutions. Reactions of sulfuric acid with these gases will form products with differing solubilities. For example, uptake of HCl by H2SO4/H2O droplets yields chlorosulfonic acid, ClSO3H (Robinson et al 1998) in solution. This may eventually decompose to thionyl- or sulfuryl chlorides, which have UV absorbances. HF will also uptake, creating fluorosulfonic acid, FSO3H, which has a greater solubility than the chloro- acid. As uptake continues, there will be many dissolved species in the cloudwaters. Baines and Delitsky (2013) showed that uptake will have a maximum at ~62 km and this is very close to the reported altitude for the mystery UV absorber in the Venus atmosphere. In addition, at very strong concentrations in lower altitude clouds, sulfuric acid will form hydrates such as H2SO4.H2O and H2SO4.4H2O which will have very different freezing behavior than sulfuric acid, with much higher freezing temperatures (Carslaw et al, 1997). Using temperature data from Venus Express from Tellmann et al (2009), and changes in H2SO4 concentrations as a function of altitude (James et al 1997), we calculate that freezing out of sulfuric acid hydrates can be significant down to as low as 56 km altitude. As a result, balloons, aircraft or other probes in the Venus atmosphere may be limited to flying below certain altitudes. Any craft flying at altitudes above ~55 km may suffer icing on the wings, propellers, balloons and instruments which could cause possible detrimental effects (thermal

  12. Characteristics of wintertime and autumn nitric acid chemistry as defined by Limb Infrared Monitor of the Stratosphere (LIMS) data

    NASA Astrophysics Data System (ADS)

    Rood, Richard B.; Douglass, Anne R.; Kaye, Jack A.; Considine, David B.

    1993-10-01

    Earlier two-dimensional (2-D) and three-dimensional (3-D) model experiments have shown that the Limb Infrared Monitor of the Stratosphere (LIMS) nitric acid data do not behave as expected from conventional gas phase chemical reactions. As contrasted to two-dimensional (2-D) model results, the 3-D model suggests that the discrepancies are at middle latitudes outside of the polar vortex, rather than at polar latitudes. Using only the data record, the characteristics of the nitric acid behavior arc further examined. The data inside the Aleutian anticyclone are examined during the January wave 1 warming. The anticyclone provides a large isolated region of air that moves from about 40°N to 60°N during the warming. Ozone remains approximately constant during this transit, while nitric acid increases more than 1 parts per billion by volume (ppbv). Both ozone and water vapor fields develop a wave 1 structure during the warming, as expected. Nitric acid, which is also expected to develop a wave 1 signal, develops a prominent wave 2 structure. This structure is observed between 50 and 5 mbar. A prominent feature of the nitric acid field is the persistent "bending" of contours due to strong meridional flow. Since these contours persist, instead of aligning with the flow, there must be chemical processes maintaining the nitric acid with timescales shorter than the advective timescale. The time constant for this chemical process ranges from approximately 1 day at 70°N to about 4 days at 30°N. When the time constant is used in the 3-D model, all of the basic characteristics of the observations are simulated. It is not clear what chemical mechanisms are responsible for this behavior. There is a strong relationship between the insolation and the shortcomings of the nitric acid simulations. Heterogeneous reactions on background aerosols are considered, but their spatial, temporal, and chemical characteristics are not clearly consistent with the needed changes in the chemistry

  13. The Chemistry of Polymers, Proteins, and Nucleic Acids: A Short Course on Macromolecules for Secondary Schools.

    ERIC Educational Resources Information Center

    Lulav, Ilan; Samuel, David

    1985-01-01

    Describes a unit on macromolecules that has been used in the 12th grade of many Israeli secondary schools. Topic areas in the unit include synthetic polymers, biological macromolecules, and nucleic acids. A unit outline is provided in an appendix. (JN)

  14. Tetramic and Tetronic Acids as Scaffolds in Bioinorganic and Bioorganic Chemistry

    PubMed Central

    Athanasellis, G.; Igglessi-Markopoulou, O.; Markopoulos, J.

    2010-01-01

    Tetramic and tetronic acids are naturally occurring molecules with a variety of biological activities. In this review article, we present the general strategies for the synthesis of these compounds and we reveal the functionalized groups that are responsible for their properties. We also set out their coordinating modes with up-to-date bibliographical references. PMID:20508811

  15. Similar bacterial community composition in acidic mining lakes with different pH and lake chemistry.

    PubMed

    Kampe, Heike; Dziallas, Claudia; Grossart, Hans-Peter; Kamjunke, Norbert

    2010-10-01

    As extreme environmental conditions strongly affect bacterial community composition (BCC), we examined whether differences in pH-even at low pH-and in iron and sulfate concentrations lead to changes in BCC of acidic mining lakes. Thereby, we tested the following hypotheses: (1) diversity of the bacterial community in acidic lakes decreases with reducing pH, (2) BCC differs between epilimnion and hypolimnion, and (3) BCC in extremely acidic environments does not vary much over time. Therefore, we investigated the BCC of three acidic lakes with different pH values (2.3, 2.7, and 3.2) by denaturing gradient gel electrophoresis (DGGE) and subsequent sequencing of DGGE bands as well as catalyzed reporter deposition-FISH (CARD-FISH). BCC did not significantly vary among the studied lakes nor differ much between water layers. In contrast, BCC significantly changed over time, which is contradictory to our hypotheses. Bacterial communities were dominated by Alpha-, Beta-, and Gammaproteobacteria, whereas Actino- and Acidobacteria rarely occurred. Cell numbers of both free and attached bacteria were positively related to DOC concentration. Overall, low pH and extreme chemical conditions of the studied lakes led to similar assemblages of bacteria with pronounced temporal differences. This notion indicates that temporal changes in environmental conditions including food web structure also affect unique communities of bacteria thriving at low pH.

  16. Some instrumental methods applied in food chemistry to characterise lactulose and lactobionic acid.

    PubMed

    Bisinella, Radla Zabian Bassetto; Ribeiro, Jéssica Caroline Bigaski; de Oliveira, Cristina Soltovski; Colman, Tiago André Denck; Schnitzler, Egon; Masson, Maria Lúcia

    2017-04-01

    Lactose is obtained as a by-product from whey. It is a source of several derivatives, including lactulose and lactobionic acid. These two compounds were analysed by using the following techniques: thermogravimetry/derivative thermogravimetry (TG/DTG), differential scanning calorimetry coupled with optical microscope (DSC-thermomicroscopy), infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). The DSC technique coupled with microscopy made it possible to observe that the lactobionic acid showed several thermal events upon decomposition, which occurred at temperatures higher than 50°C. The lactulose began to decompose above 180°C. The DSC curve was used to calculate the purity of the lactulose (according to Van't Hoff equation), which was 98% and the melting point peak occurred at 171°C. The lactulose showed crystalline behaviour that was different to that of the lactobionic acid, which was attributed to its high hygroscopicity. Purity of lactobionic acid was not calculated because the decomposition occurred in consecutive stages.

  17. Developing phospha-Stork chemistry induced by a borane Lewis acid.

    PubMed

    Hasegawa, Yasuharu; Daniliuc, Constantin G; Kehr, Gerald; Erker, Gerhard

    2014-11-03

    Bulky vinyl phosphanes undergo carbon-carbon coupling with aryl aldehydes with the help of the Lewis acid B(C6F5)3 to give isolable methylene phosphonium products. Dimesityl(vinyl)phosphane undergoes a phospha-Stork reaction with bulky enones efficiently catalyzed by B(C6F5)3 to eventually yield the corresponding substituted cyclobutane products.

  18. Grass roots chemistry: meta-Tyrosine, an herbicidal nonprotein amino acid

    PubMed Central

    Bertin, Cécile; Weston, Leslie A.; Huang, Tengfang; Jander, Georg; Owens, Thomas; Meinwald, Jerrold; Schroeder, Frank C.

    2007-01-01

    Fine fescue grasses displace neighboring plants by depositing large quantities of an aqueous phytotoxic root exudate in the soil rhizosphere. Via activity-guided fractionation, we have isolated and identified the nonprotein amino acid m-tyrosine as the major active component. m-Tyrosine is significantly more phytotoxic than its structural isomers o- and p-tyrosine. We show that m-tyrosine exposure results in growth inhibition for a wide range of plant species and propose that the release of this nonprotein amino acid interferes with root development of competing plants. Acid hydrolysis of total root protein from Arabidopsis thaliana showed incorporation of m-tyrosine, suggesting this as a possible mechanism of phytotoxicity. m-Tyrosine inhibition of A. thaliana root growth is counteracted by exogenous addition of protein amino acids, with phenylalanine having the most significant effect. The discovery of m-tyrosine, as well as a further understanding of its mode(s) of action, could lead to the development of biorational approaches to weed control. PMID:17940026

  19. Assessment of the Effects Exerted by Acid and Alkaline Solutions on Bone: Is Chemistry the Answer?

    PubMed

    Amadasi, Alberto; Camici, Arianna; Porta, Davide; Cucca, Lucia; Merli, Daniele; Milanese, Chiara; Profumo, Antonella; Rassifi, Nabila; Cattaneo, Cristina

    2017-02-01

    The treatment of corpses with extremely acid or basic liquids is sometimes performed in criminal contexts. A thorough characterization by chemical analysis may provide further help to macroscopic and microscopic analysis; 63 porcine bone samples were treated with solutions at different pH (1-14) for immersion periods up to 70 days, as well as in extremely acidic sulfuric acid solutions (9 M/18 M) and extremely basic sodium hydroxide. Inductively coupled optical emission spectrometry (ICP-OES)/plasma mass spectrometry (ICP-MS), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM) showed that only the sulfuric acid solution 18 M was able to completely dissolve the sample. In addition, chemical analysis allowed to recognize the contact between bone and substances. Hydrated calcium sulfate arose from extreme pH. The possibility of detecting the presence of human material within the residual solution was demonstrated, especially with FT-IR, ICP-OES, and EDX.

  20. Secondary porosity revisited: The chemistry of feldspar dissolution by carboxylic acids and anions

    SciTech Connect

    Stoessell, R.K. ); Pittman, E.D. )

    1990-12-01

    Carboxylic acids in subsurface waters have been proposed as agents for dissolving feldspars and complexing aluminum to create secondary porosity in sandstones. Previously published experimental work indicated high aluminum mobility in the presence of carboxylic acid solutions. In order to further evaluate aluminum mobility, alkali feldspar dissolution experiments were run at 100C and 300 bars in the presence of mono- and dicarboxylic acids and their anions. Experimental results imply that under reservoir conditions, aluminum-organic anion complexes are insignificant for acetate and propionate and possibly significant for oxalate and malonate. Propionate appeared to inhibit alkali feldspar dissolution and, hence, may retard aluminum mobility. Dissolution of feldspar in the presence of oxalic and acetic acid can be explained by enhanced dissolution kinetics and greater aluminum mobility under low-pH conditions. The general absence of such low-pH fluids in subsurface reservoirs makes this an unlikely mechanism for creating secondary porosity. Also, the thermal instability of oxalate and malonate limits their aluminum-complexing potential in reservoirs at temperatures above 100C.

  1. Ultrasound in fatty acid chemistry: synthesis of a 1-pyrroline fatty acid ester isomer from methyl ricinoleate.

    PubMed

    Lie Ken Jie, M S; Syed-Rahmatullah, M S; Lam, C K; Kalluri, P

    1994-12-01

    A novel 1-pyrroline fatty acid ester isomer (viz. 8-5-hexyl-1-pyrrolin-2-yl) octanoate) has been synthesized from methyl ricinoleate by two routes with an overall yield of 42 and 30%, respectively. Most of the reactions are carried out under concomitant ultrasonic irradiation (20 KHz, ca. 53 watts/cm2). Under such a reaction condition, the reaction time is considerably shortened, and product yields are high. Dehydrobromination under concomitant ultrasonic irradiation of methyl 9, 10-dibromo-12-hydroxyoctadecanoate with KOH in EtOH furnishes methyl 12-hydroxy-9-octadecynoate (66%) within 15 min. Hydration of the latter under ultrasound with mercury(II)acetate in aqueous tetrahydrofuran yields exclusively methyl 12-hydroxy-9-oxo-octadecanoate (95%) in 30 min. The hydroxy group in the latter compound is transformed to the azido function via the mesylate, and treatment of the azido-oxo intermediate (methyl 12-azido-9-oxooctadecanoate) with Ph3P under ultrasonic irradiation furnishes the requisite 1-pyrroline fatty acid ester (77%). The same azido-oxo intermediate has also been obtained by the oxidation of methyl 12-azido-9-cis-octadecenoate using benzoquinone and a catalytic amount of Pd(II)chloride in aqueous tetrahydrofuran under concomitant ultrasonic irradiation (90 min) to give the product in 45% yield. The latter reaction does not take place even under prolonged silent stirring of the reaction mixture.

  2. Integration of Environmental Analytical Chemistry with Environmental Law: The Development of a Problem-Based Laboratory

    NASA Astrophysics Data System (ADS)

    Cancilla, Devon A.

    2001-12-01

    Environmental chemists face difficult challenges related to generating, interpreting, and communicating complex chemical data in a manner understandable by nonchemists. For this reason, it is essential that environmental chemistry students develop the skills necessary not only to collect and interpret complex data sets, but also to communicate their findings in a credible manner in nonscientific forums. Key to this requirement is an understanding of the quality assurance/quality control (QA/QC) elements used to support specific findings. This paper describes the development of a problem-based undergraduate environmental analytical chemistry laboratory and its integration with an undergraduate environmental law course. The course is designed to introduce students to the principles of performance-based analytical methods and the use of environmental indicators to perform environmental assessments. Conducting a series of chemical and toxicological tests, chemistry students perform an environmental assessment on the watershed of the mythical City of Rowan. Law students use these assessments to develop legal arguments under both the Safe Drinking Water Act and the Clean Water Act.

  3. Investigation of nonfouling polypeptides of poly(glutamic acid) with lysine side chains synthesized by EDC·HCl/HOBt chemistry.

    PubMed

    Yang, Qinghua; Li, Wenchen; Wang, Longgang; Wang, Guangzhi; Wang, Zhen; Liu, Lingyun; Chen, Shengfu

    2014-01-01

    Nonfouling polypeptides with homogenous alternating charges draw peoples' attentions for their potential capability in biodegradation. Homogenous glutamic acid (E) and lysine (K) polypeptides were proposed and synthesized before. In this work, a new polypeptide formed by poly(glutamic acid) with lysine side chains (poly(E)-K) was synthesized by facile EDC·HCl/HOBt chemistry and investigated. Results show that these polypeptides also have good nonspecific protein resistance determined by enzyme-linked immunosorbent assay. The lowest nonspecific adsorption of the model proteins, anti-IgG and fibrinogen (Fg), on the self-assembling monolayers (SAMs) surface of poly(E)-K was only 3.3 ± 1.8 and 4.4 ± 1.6%, respectively, when protein adsorption on tissue culture polystyrene surface was set as 100%. And, the relative nonspecific protein adsorption increases when the polypeptide molecular weight increases due to the repression of low density polymer brushes. Moreover, almost no obvious cytotoxicity and hemolytic activity in vitro were detected. This work suggests that polypeptides with various formats of homogenous balanced charges could achieve excellent nonspecific protein resistance, which might be the intrinsic reason for the coexistence of high concentration serum proteins in blood.

  4. Determination of Quantum Chemistry Based Force Fields for Molecular Dynamics Simulations of Aromatic Polymers

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Ab initio quantum chemistry calculations for model molecules can be used to parameterize force fields for molecular dynamics simulations of polymers. Emphasis in our research group is on using quantum chemistry-based force fields for molecular dynamics simulations of organic polymers in the melt and glassy states, but the methodology is applicable to simulations of small molecules, multicomponent systems and solutions. Special attention is paid to deriving reliable descriptions of the non-bonded and electrostatic interactions. Several procedures have been developed for deriving and calibrating these parameters. Our force fields for aromatic polyimide simulations will be described. In this application, the intermolecular interactions are the critical factor in determining many properties of the polymer (including its color).

  5. Chemistry Is in the News: Taxonomy of authentic news media-based learning activities1

    NASA Astrophysics Data System (ADS)

    Glaser, Rainer E.; Carson, Kathleen M.

    2005-09-01

    A brief history is given of approaches that aim at achieving a connectedness of the content of organic chemistry courses to real world issues. Recently, such approaches have relied more and more on online media resources, the tools of the Internet and the World Wide Web. We propose a six-level taxonomy of ‘authentic news media-based learning activities’ to provide a conceptual framework for the description and discussion of such approaches. The Chemistry Is in the News project was designed to allow students to draw explicit connections between the course content and real world issues in ways that engage the students in a full range of cognitive skills. The activities consisted in the study, creation, and peer review of news portfolios by student collaborative groups. A news portfolio consists of an authentic news article taken from the popular press with interpretive comments and questions.

  6. Chemistry of natural fuel: Use of wastes of synthetic fatty acid production for obtaining water-bitumen emulsions

    SciTech Connect

    Syroezhko, A.M.; Antipova, E.I.; Paukku, A.N.

    1995-12-10

    The possibility of producing water-emulsion waterproofing mastic and waterproofing coating based on bitumen, rubber crumb, and bottoms from production of synthetic fatty acids was studied. The physicochemical properties (softening point, ductility, sorptive properties, and friability) of the waterproofing coating based on a water-emulsion mastic were measured.

  7. Presidential Green Chemistry Challenge: 2011 Small Business Award

    EPA Pesticide Factsheets

    Presidential Green Chemistry Challenge 2011 award winner, BioAmber, developed an integrated technology to produce large, commercial quantities of succinic acid by bacterial fermentation, replacing petroleum-based feedstocks.

  8. Nitrogen Oxides in the Nocturnal Boundary Layer: Chemistry of Nitrous Acid (HONO) and the Nitrate Radical (N03)

    SciTech Connect

    Jochen Stutz

    2005-05-24

    dependent. Measurements at one altitude, for example at the ground, where most air quality monitoring stations are located, are not representative for the rest of the NBL. Our model also revealed that radical chemistry is, in general, altitude dependent at night. We distinguish three regions: an unreactive, NO rich, ground layer; an upper, O3 and NO3 dominated layer, and a reactive mixing layer, where RO2 radicals are mixed from aloft with NO from the ground. In this reactive layer an active radical chemistry and elevated OH radical levels can be found. The downward transport of N2O5 and HO2NO2, followed by their thermal decay, was also identified as a radical source in this layer. Our observations also gave insight into the formation of HONO in the NBL. Based on our field experiments we were able to show that the NO2 to HONO conversion was relative humidity dependent. While this fact was well known, we found that it is most likely the uptake of HONO onto surfaces which is R.H. dependent, rather than the NO2 to HONO conversion. This finding led to the proposal of a new NO2 to HONO conversion mechanism, which is based on solid physical chemical principles. Noteworthy is also the observation of enhanced NO2 to HONO conversion during a dust storm event in Phoenix. The final activity in our project investigated the influence of the urban canopy, i.e. building walls and surfaces, on nocturnal chemistry. For the first time the surface area of a city was determined based on a Geographical Information System database of the city of Santa Monica. The surface to volume areas found in this study showed that, in the 2 lower part of the NBL, buildings provide a much larger surface area than the aerosol. In addition, buildings take up a considerable amount of the volume near the ground. The expansion of our model and sensitivity studies based on the Santa Monica data revealed that the surface area of buildings considerably influences HONO levels in urban areas. The volume reduction leads

  9. Extending Halogen-based Medicinal Chemistry to Proteins: IODO-INSULIN AS A CASE STUDY.

    PubMed

    El Hage, Krystel; Pandyarajan, Vijay; Phillips, Nelson B; Smith, Brian J; Menting, John G; Whittaker, Jonathan; Lawrence, Michael C; Meuwly, Markus; Weiss, Michael A

    2016-12-30

    Insulin, a protein critical for metabolic homeostasis, provides a classical model for protein design with application to human health. Recent efforts to improve its pharmaceutical formulation demonstrated that iodination of a conserved tyrosine (Tyr(B26)) enhances key properties of a rapid-acting clinical analog. Moreover, the broad utility of halogens in medicinal chemistry has motivated the use of hybrid quantum- and molecular-mechanical methods to study proteins. Here, we (i) undertook quantitative atomistic simulations of 3-[iodo-Tyr(B26)]insulin to predict its structural features, and (ii) tested these predictions by X-ray crystallography. Using an electrostatic model of the modified aromatic ring based on quantum chemistry, the calculations suggested that the analog, as a dimer and hexamer, exhibits subtle differences in aromatic-aromatic interactions at the dimer interface. Aromatic rings (Tyr(B16), Phe(B24), Phe(B25), 3-I-Tyr(B26), and their symmetry-related mates) at this interface adjust to enable packing of the hydrophobic iodine atoms within the core of each monomer. Strikingly, these features were observed in the crystal structure of a 3-[iodo-Tyr(B26)]insulin analog (determined as an R6 zinc hexamer). Given that residues B24-B30 detach from the core on receptor binding, the environment of 3-I-Tyr(B26) in a receptor complex must differ from that in the free hormone. Based on the recent structure of a "micro-receptor" complex, we predict that 3-I-Tyr(B26) engages the receptor via directional halogen bonding and halogen-directed hydrogen bonding as follows: favorable electrostatic interactions exploiting, respectively, the halogen's electron-deficient σ-hole and electronegative equatorial band. Inspired by quantum chemistry and molecular dynamics, such "halogen engineering" promises to extend principles of medicinal chemistry to proteins.

  10. 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)

  11. 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)

  12. Precipitation-chemistry measurements from the California Acid Deposition Monitoring Program, 1985-1990

    USGS Publications Warehouse

    Blanchard, Charles L.; Tonnessen, Kathy A.

    1993-01-01

    The configuration of the California Acid Deposition Monitoring Program (CADMP) precipitation network is described and quality assurance results summarized. Comparison of CADMP and the National Acid Deposition Program/National Trends Network (NADP/NTN) data at four parallel sites indicated that mean depth-weighted differences were less than 3 μeq ℓ−1 for all ions, being statistically significant for ammonium, sulfate and hydrogen ion. These apparently small differences were 15–30% of the mean concentrations of ammonium, sulfate and hydrogen ion. Mean depth-weighted concentrations and mass deposition rates for the period 1985–1990 are summarized; the latter were highest either where concentrations or precipitation depths were relatively high.

  13. 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.

  14. Vanadium-fulvic acid chemistry: conformational and binding studies by electron spin probe techniques

    NASA Astrophysics Data System (ADS)

    Templeton, G. Daniel, III; Chasteen, N. Dennis

    1980-05-01

    Two fractions of soil fulvic acid (FA) were separated by gel filtration chromatography. An observed increase in volume of the heavier fraction (FA I) with increasing pH was attributed to aggregation, intramolecular negative charge repulsions and the rupture of hydrogen bonds, which control molecular conformation. Optical absorption properties and elemental analyses of both fractions were determined. The stability constants and stoichiometries of FA complexes with vanadyl, VO 2+, at pH 5.0 and ionic strength of 0.04 M were measured by electron paramagnetic resonance (EPR) spectroscopy. EPR spectra of model VO 2+ complexes with phthalic and salicylic acids, which are the probable functional groups present in FA, are identical to those of the VO 2+-FA complexes. Aggregation of FA I occurs in the presence of VO 2+ to form a complex that can be approximated as '(VO) 2(FA I) 6'. The average site distance between vanadyl ions in this complex is shown to be greater than 1.2 nm. EPR parameters for FA I suggest binding by carboxylate groups. These parameters are compared with those of other vanadyl complexes with fulvic and humic acids reported by others. Reduction of VO 3- to VO 2+ by these materials is discussed.

  15. 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

  16. Surface modification of poly(D,L-lactic acid) scaffolds for orthopedic applications: a biocompatible, nondestructive route via diazonium chemistry.

    PubMed

    Mahjoubi, Hesameddin; Kinsella, Joseph M; Murshed, Monzur; Cerruti, Marta

    2014-07-09

    Scaffolds made with synthetic polymers such as polyesters are commonly used in bone tissue engineering. However, their hydrophobicity and the lack of specific functionalities make their surface not ideal for cell adhesion and growth. Surface modification of these materials is thus crucial to enhance the scaffold's integration in the body. Different surface modification techniques have been developed to improve scaffold biocompatibility. Here we show that diazonium chemistry can be used to modify the outer and inner surfaces of three-dimensional poly(D,L-lactic acid) (PDLLA) scaffolds with phosphonate groups, using a simple two-step method. By changing reaction time and impregnation procedure, we were able to tune the concentration of phosphonate groups present on the scaffolds, without degrading the PDLLA matrix. To test the effectiveness of this modification, we immersed the scaffolds in simulated body fluid, and characterized them with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman, and infrared spectroscopy. Our results showed that a layer of hydroxyapatite particles was formed on all scaffolds after 2 and 4 weeks of immersion; however, the precipitation was faster and in larger amounts on the phosphonate-modified than on the bare PDLLA scaffolds. Both osteogenic MC3T3-E1 and chondrogenic ATDC5 cell lines showed increased cell viability/metabolic activity when grown on a phosphonated PDLLA surface in comparison to a control PDLLA surface. Also, more calcium-containing minerals were deposited by cultures grown on phosphonated PDLLA, thus showing the pro-mineralization properties of the proposed modification. This work introduces diazonium chemistry as a simple and biocompatible technique to modify scaffold surfaces, allowing to covalently and homogeneously bind a number of functional groups without degrading the scaffold's polymeric matrix.

  17. 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.

  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.

  19. Graphene-based materials: fabrication and application for adsorption in analytical chemistry.

    PubMed

    Wang, Xin; Liu, Bo; Lu, Qipeng; Qu, Qishu

    2014-10-03

    Graphene, a single layer of carbon atoms densely packed into a honeycomb crystal lattice with unique electronic, chemical, and mechanical properties, is the 2D allotrope of carbon. Owing to the remarkable properties, graphene and graphene-based materials are likely to find potential applications as a sorbent in analytical chemistry. The current review focuses predominantly on the recent development of graphene-based materials and demonstrates their enhanced performance in adsorption of organic compounds, metal ions, and solid phase extraction as well as in separation science since mostly 2012.

  20. Boronic Acid-Based Approach for Separation and Immobilization of Glycoproteins and Its Application in Sensing

    PubMed Central

    Wang, Xiaojin; Xia, Ning; Liu, Lin

    2013-01-01

    Glycoproteins influence a broad spectrum of biological processes including cell-cell interaction, host-pathogen interaction, or protection of proteins against proteolytic degradation. The analysis of their glyco-structures and concentration levels are increasingly important in diagnosis and proteomics. Boronic acids can covalently react with cis-diols in the oligosaccharide chains of glycoproteins to form five- or six-membered cyclic esters. Based on this interaction, boronic acid-based ligands and materials have attracted much attention in both chemistry and biology as the recognition motif for enrichment and chemo/biosensing of glycoproteins in recent years. In this work, we reviewed the progress in the separation, immobilization and detection of glycoproteins with boronic acid-functionalized materials and addressed its application in sensing. PMID:24141187

  1. Teaching Green and Sustainable Chemistry: A Revised One-Semester Course Based on Inspirations and Challenges

    ERIC Educational Resources Information Center

    Marteel-Parrish, Anne E.

    2014-01-01

    An elective course, "Toward the Greening of Our Minds": Green and Sustainable Chemistry, has been offered at Washington College since 2005. This new course without laboratory is designed for chemistry and biology majors and minors who have previously taken two semesters of general chemistry and organic chemistry. Due to the popularity of…

  2. Adsorption and thermal chemistry of formic acid on clean and oxygen-predosed Cu(110) single-crystal surfaces revisited

    NASA Astrophysics Data System (ADS)

    Yao, Yunxi; Zaera, Francisco

    2016-04-01

    The thermal chemistry of formic acid on clean and oxygen-predosed Cu(110) single-crystal surfaces was studied under ultrahigh-vacuum (UHV) conditions by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Key results reported in the past were confirmed, including the partial switchover from H2 to H2O desorption upon oxygen addition on the surface and the development of a second decomposition regime at 420 K, in addition to the one observed at 460 K on the clean substrate. In addition, new observations were added, including the previously missed desorption of H2 at 420 K and the existence of a normal kinetic isotope effect in both TPD peaks. Peak fitting of the XPS data afforded the identification of an asymmetric geometry for the formate intermediate, which was established to form by 200 K, and the presence of coadsorbed molecular formic acid up to the temperatures of decomposition, probably in a second layer and held by hydrogen bonding. Quantitative analysis of the TPD data indicated a one-to-one correspondence between the increase in oxygen coverage beyond θO = 0.5 ML and a decrease in formic acid uptake that mainly manifests itself in a decrease in the decomposition seen in the 460 K TPD peak. All these observations were interpreted in terms of a simple decomposition mechanism involving hydrogen abstraction from adsorbed formate species, possibly aided by coadsorbed oxygen, and a change in reaction activation energy as a function of the structure of the oxygen overlayer, which reverts from a O-c(6 × 2) structure at high oxygen coverages to the O-(2 × 1) order seen at θO = 0.5 ML.

  3. Groundtruthing and potential for predicting acid deposition impacts in headwater streams using bedrock geology, GIS, angling, and stream chemistry.

    PubMed

    Kirby, C S; McInerney, B; Turner, M D

    2008-04-15

    Atmospheric acid deposition is of environmental concern worldwide, and the determination of impacts in remote areas can be problematic. Rainwater in central Pennsylvania, USA, has a mean pH of approximately 4.4. Bedrock varies dramatically in its ability to neutralize acidity. A GIS database simplified reconnaissance of non-carbonate bedrock streams in the Valley and Ridge Province and identified potentially chronically impacted headwater streams, which were sampled for chemistry and brook trout. Stream sites (n=26) that originate in and flow through the Tuscarora had a median pH of 5.0 that was significantly different from other formations. Shawangunk streams (n=6) and non-Tuscarora streams (n=20) had a median pH of 6.0 and 6.3, respectively. Mean alkalinity for non-Tuscarora streams (2.6 mg/L CaCO(3)) was higher than the mean for Tuscarora streams (0.5 mg/L). Lower pH and alkalinity suggest that the buffering capability of the Tuscarora is inferior to that of adjacent sandstones. Dissolved aluminum concentrations were much higher for Tuscarora streams (0.2 mg/L; approximately the lethal limit for brook trout) than for non-Tuscarora streams (0.03 mg/L) or Shawangunk streams (0.02 mg/L). Hook-and-line methods determined the presence/absence of brook trout in 47 stream reaches with suitable habitat. Brook trout were observed in 21 of 22 non-Tuscarora streams, all 6 Shawangunk streams, and only 9 of 28 Tuscarora stream sites. Carefully-designed hook-and-line sampling can determine the presence or absence of brook trout and help confirm biological impacts of acid deposition. 15% of 334 km of Tuscarora stream lengths are listed as "impaired" due to atmospheric deposition by the Pennsylvania Department of Environmental Protection. 65% of the 101 km of Tuscarora stream lengths examined in this study were impaired.

  4. Reductive alkylation and sequential reductive alkylation-click chemistry for on-solid-support modification of pyrrolidinyl peptide nucleic acid.

    PubMed

    Ditmangklo, Boonsong; Boonlua, Chalothorn; Suparpprom, Chaturong; Vilaivan, Tirayut

    2013-04-17

    A methodology for the site-specific attachment of fluorophores to the backbone of pyrrolidinyl peptide nucleic acids (PNAs) with an α/β-backbone derived from D-prolyl-(1S,2S)-2-aminocyclopentanecarboxylic acid (acpcPNA) has been developed. The strategy involves a postsynthetic reductive alkylation of the aldehyde-containing labels onto the acpcPNA that was previously modified with (3R,4S)-3-aminopyrrolidine-4-carboxylic acid on the solid support. The reductive alkylation reaction is remarkably efficient and compatible with a range of reactive functional groups including Fmoc-protected amino, azide, and alkynes. This allows further attachment of readily accessible carboxyl-, alkyne-, or azide-containing labels via amide bond formation or Cu-catalyzed azide-alkyne cycloaddition (CuAAC, also known as click chemistry). The label attached in this way does not negatively affect the affinity and specificity of the pairing of the acpcPNA to its DNA target. Applications of this methodology in creating self-reporting pyrene- and thiazole orange-labeled acpcPNA probes that can yield a change in fluorescence in response to the presence of the correct DNA target have also been explored. A strong fluorescence enhancement was observed with thiazole orange-labeled acpcPNA in the presence of DNA. The specificity could be further improved by enzymatic digestion with S1 nuclease, providing a 9- to 60-fold fluorescence enhancement with fully complementary DNA and a less than 3.5-fold enhancement with mismatched DNA targets.

  5. 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…

  6. A clinical approach to acid-base conundrums.

    PubMed

    Garrubba, Carl; Truscott, Judy

    2016-04-01

    Acid-base disorders can provide essential clues to underlying patient conditions. This article provides a simple, practical approach to identifying simple acid-base disorders and their compensatory mechanisms. Using this stepwise approach, clinicians can quickly identify and appropriately treat acid-base disorders.

  7. 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…

  8. Facile preparation of biocompatible sulfhydryl cotton fiber-based sorbents by "thiol-ene" click chemistry for biological analysis.

    PubMed

    He, Xiao-Mei; Zhu, Gang-Tian; Zhu, Yuan-Yuan; Chen, Xi; Zhang, Zheng; Wang, Shao-Ting; Yuan, Bi-Feng; Feng, Yu-Qi

    2014-10-22

    Sulfhydryl cotton fiber (SCF) has been widely used as adsorbent for a variety of metal ions since 1971. Thanks to the abundant thiols on SCF, in this study, we reported a universal method for the facile preparation of SCF-based materials using "thiol-ene" click chemistry for the first time. With the proposed method, two types of SCF-based materials, phenylboronic acid grafted sulfhydryl cotton fiber (SCF-PBA) and zirconium phosphonate-modified sulfhydryl cotton fiber (SCF-pVPA-Zr(4+)), were successfully prepared. The grafted functional groups onto the thiol group of SCF were demonstrated by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). The prepared fibrous materials exhibited excellent fiber strength, good stability in aqueous or nonaqueous solutions, and great biocompatibility. Moreover, we developed filter-free in-pipet-tip SPE using these SCF-based materials as adsorbent for the enrichment of ribonucleosides, glycopeptides and phosphopeptides. Our results showed that SCF-PBA adsorbent can selectively capture ribonucleosides and glycopeptides from complex biological samples. And SCF-pVPA-Zr(4+) adsorbent exhibited high selectivity and capacity in the enrichment of phosphopeptides from the digestion mixture of β-casein and bovine serum albumin (BSA), as well as human serum and nonfat milk digest. Generally, the preparation strategy can be a universal method for the synthesis of other functionalized cotton-based adsorbents with special requirement in microscale biological analysis.

  9. Synthesis of goethite in solutions of artificial seawater and amino acids: a prebiotic chemistry study

    NASA Astrophysics Data System (ADS)

    Carneiro, Cristine E. A.; Ivashita, Flávio F.; de Souza, Ivan Granemann; de Souza, Cláudio M. D.; Paesano, Andrea; da Costa, Antonio C. S.; di Mauro, Eduardo; de Santana, Henrique; Zaia, Cássia T. B. V.; Zaia, Dimas A. M.

    2013-04-01

    This study investigated the synthesis of goethite under conditions resembling those of the prebiotic Earth. The artificial seawater used contains all the major elements as well as amino acids (α-Ala, β-Ala, Gly, Cys, AIB) that could be found on the prebiotic Earth. The spectroscopic methods (FT-IR, EPR, Raman), scanning electron microscopy (SEM) and X-ray diffraction showed that in any condition Gly and Cys favoured the formation of goethite, artificial seawater plus β-Ala and distilled water plus AIB favoured the formation of hematite and for the other synthesis a mixture of goethite and hematite were obtained. Thus in general no protein amino acids (β-Ala, AIB) favoured the formation of hematite. As shown by surface enhanced Raman spectroscopy (SERS) spectra the interaction between Cys and Fe3+ of goethite is very complex, involving decomposition of Cys producing sulphur, as well as interaction of carboxylic group with Fe3+. SERS spectra also showed that amino/CN and C-CH3 groups of α-Ala are interacting with Fe3+ of goethite. For the other samples the shifting of several bands was observed. However, it was not possible to say which amino acid groups are interacting with Fe3+. The pH at point of zero charge of goethites increased with artificial seawater and decreased with amino acids. SEM images showed when only goethite was synthesized the images of the samples were acicular and when only hematite was synthesized the images of the samples were spherical. SEM images for the synthesis of goethite with Cys were spherical crystal aggregates with radiating acicular crystals. The highest resonance line intensities were obtained for the samples where only hematite was obtained. Electron paramagnetic resonance (EPR) and Mössbauer spectra showed for the synthesis of goethite with artificial seawater an isomorphic substitution of iron by seawater cations. Mössbauer spectra also showed that for the synthesis goethite in distilled water plus Gly only goethite was

  10. Oleic acid-based gemini surfactants with carboxylic acid headgroups.

    PubMed

    Sakai, Kenichi; Umemoto, Naoki; Matsuda, Wataru; Takamatsu, Yuichiro; Matsumoto, Mutsuyoshi; Sakai, Hideki; Abe, Masahiko

    2011-01-01

    Anionic gemini surfactants with carboxylic acid headgroups have been synthesized from oleic acid. The hydrocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via an ester bond, and the carboxylic acid headgroups are introduced to the cis double bond of oleic acid via disuccinyl units. The surfactants exhibit pH-dependent protonation-deprotonation behavior in aqueous solutions. In alkaline solutions (pH 9 in the presence of 10 mmol dm(-3) NaCl as the background electrolyte), the surfactants can lower the surface tension as well as form molecular assemblies, even in the region of low surfactant concentrations. Under acidic (pH 3) or neutral (pH 6-7) conditions, the surfactants are intrinsically insoluble in aqueous media and form a monolayer at the air/water interface. In this study, we have investigated physicochemical properties such as the function of the hydrocarbon chain length by means of static surface tension, pyrene fluorescence, dynamic light scattering, surface pressure-area isotherms, and infrared external reflection measurements.

  11. Iron Oxide Surface Chemistry: Effect of Chemical Structure on Binding in Benzoic Acid and Catechol Derivatives.

    PubMed

    Korpany, Katalin V; Majewski, Dorothy D; Chiu, Cindy T; Cross, Shoronia N; Blum, Amy Szuchmacher

    2017-03-13

    The excellent performance of functionalized iron oxide nanoparticles (IONPs) in nanomaterial and biomedical applications often relies on achieving the attachment of ligands to the iron oxide surface both in sufficient number and with proper orientation. Toward this end, we determine relationships between the ligand chemical structure and surface binding on magnetic IONPs for a series of related benzoic acid and catechol derivatives. Ligand exchange was used to introduce the model ligands, and the resultant nanoparticles were characterized using Fourier transform infrared-attenuated internal reflectance spectroscopy, transmission electron microscopy, and nanoparticle solubility behavior. An in-depth analysis of ligand electronic effects and reaction conditions reveals that the nature of ligand binding does not solely depend on the presence of functional groups known to bind to IONPs. The structure of the resultant ligand-surface complex was primarily influenced by the relative positioning of hydroxyl and carboxylic acid groups within the ligand and whether or not HCl(aq) was added to the ligand-exchange reaction. Overall, this study will help guide future ligand-design and ligand-exchange strategies toward realizing truly custom-built IONPs.

  12. Old acid, new chemistry. Negative metal anions generated from alkali metal oxalates and others.

    PubMed

    Curtis, Sharon; Renaud, Justin; Holmes, John L; Mayer, Paul M

    2010-11-01

    A brief search in Sci Finder for oxalic acid and oxalates will reward the researcher with a staggering 129,280 hits. However, the generation of alkali metal and silver anions via collision-induced dissociation of the metal oxalate anion has not been previously been reported, though Tian and coworkers recently investigated the dissociation of lithium oxalate. The exothermic decomposition of alkali metal oxalate anion to carbon dioxide in the collision cell of a triple quadrupole mass spectrometer leaves no place for the electron to reside, resulting in a double electron-transfer reaction to produce an alkali metal anion. This reaction is facilitated by the negative electron affinity of carbon dioxide and, as such, the authors believe that metal oxalates are potentially unique in this respect. The observed dissociation reactions for collision with argon gas (1.7-1.8 × 10(-3) mbar) for oxalic acid and various alkali metal oxalates are discussed and summarized. Silver oxalate is also included to demonstrate the propensity of this system to generate transition-metal anions, as well.

  13. Scope and Limitations of Fmoc Chemistry SPPS-Based Approaches to the Total Synthesis of Insulin Lispro via Ester Insulin.

    PubMed

    Dhayalan, Balamurugan; Mandal, Kalyaneswar; Rege, Nischay; Weiss, Michael A; Eitel, Simon H; Meier, Thomas; Schoenleber, Ralph O; Kent, Stephen B H

    2017-01-31

    We have systematically explored three approaches based on 9-fluorenylmethoxycarbonyl (Fmoc) chemistry solid phase peptide synthesis (SPPS) for the total chemical synthesis of the key depsipeptide intermediate for the efficient total chemical synthesis of insulin. The approaches used were: stepwise Fmoc chemistry SPPS; the "hybrid method", in which maximally protected peptide segments made by Fmoc chemistry SPPS are condensed in solution; and, native chemical ligation using peptide-thioester segments generated by Fmoc chemistry SPPS. A key building block in all three approaches was a Glu[O-β-(Thr)] ester-linked dipeptide equipped with a set of orthogonal protecting groups compatible with Fmoc chemistry SPPS. The most effective method for the preparation of the 51 residue ester-linked polypeptide chain of ester insulin was the use of unprotected peptide-thioester segments, prepared from peptide-hydrazides synthesized by Fmoc chemistry SPPS, and condensed by native chemical ligation. High-resolution X-ray crystallography confirmed the disulfide pairings and three-dimensional structure of synthetic insulin lispro prepared from ester insulin lispro by this route. Further optimization of these pilot studies could yield an efficient total chemical synthesis of insulin lispro (Humalog) based on peptide synthesis by Fmoc chemistry SPPS.

  14. Geothermal surface alteration of basalts, Krýsuvík Iceland—Alteration mineralogy, water chemistry and the effects of acid supply on the alteration process

    NASA Astrophysics Data System (ADS)

    Markússon, Sigurdur H.; Stefánsson, Andri

    2011-09-01

    The geothermal surface alteration of basalts and associated water chemistry at Krýsuvík, SW Iceland were studied. The geothermal area was characterised with zones of intensive surface alteration, steam vents, mud pots and hot springs. The steam-heated geothermal surface waters had pH values between 1.69 and 7.67 and total dissolved solid (TDS) concentrations between 154 and 6660 ppm, with Cl and SO 4 concentration decreasing and increasing with decreasing pH, respectively. Alteration mineral assemblages observed were strongly associated with the surface intensity. In areas of most intensive activity the basaltic rocks were altered to amorphous silica, anatase and pyrite with a crust of native sulphur at the surface. With decreased activity, kaolinite became important, as well as iron oxyhydroxides and oxides. On the flanks of the area montmorillonite was the predominant alteration product. Based on these observations the surface geothermal activity was divided into three groups: (1) high activity areas with active steam vents and mud pots and intensive acid leaching, (2) medium activity areas where the ground is hot, steam vents and mud pots are uncommon and the surface alteration is less intensive and (3) low activity areas on the margins of the surface geothermal activity. The primary factors influencing the steam-heated acid sulphate alteration of basalts included the redox state (oxidation front), supply of acids and pH, and the extent of reaction. The formation of iron- and sulphur-containing minerals and the respective elemental mobility depended on the redox conditions with pyrite formation under reduced conditions and goethite and/or hematite under oxidised conditions. At low pH, Ca, Mg, K and Na were mobile and leached out, whereas Fe, Ti and Al and to a large degree Si were retained in the alteration product. At higher pH values > 5 the mobility of Ca, Mg, K and Na was reduced due to the formation of clays.

  15. 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.

  16. Applications of monolithic solid-phase extraction in chromatography-based clinical chemistry assays.

    PubMed

    Bunch, Dustin R; Wang, Sihe

    2013-04-01

    Complex matrices, for example urine, serum, plasma, and whole blood, which are common in clinical chemistry testing, contain many non-analyte compounds that can interfere with either detection or in-source ionization in chromatography-based assays. To overcome this problem, analytes are extracted by protein precipitation, solid-phase extraction (SPE), and liquid-liquid extraction. With correct chemistry and well controlled material SPE may furnish clean specimens with consistent performance. Traditionally, SPE has been performed with particle-based adsorbents, but monolithic SPE is attracting increasing interest of clinical laboratories. Monoliths, solid pieces of stationary phase, have bimodal structures consisting of macropores, which enable passage of solvent, and mesopores, in which analytes are separated. This structure results in low back-pressure with separation capabilities similar to those of particle-based adsorbents. Monoliths also enable increased sample throughput, reduced solvent use, varied support formats, and/or automation. However, many of these monoliths are not commercially available. In this review, application of monoliths to purification of samples from humans before chromatography-based assays will be critically reviewed.

  17. A comprehensive review in current developments of benzothiazole-based molecules in medicinal chemistry.

    PubMed

    Keri, Rangappa S; Patil, Mahadeo R; Patil, Siddappa A; Budagumpi, Srinivasa

    2015-01-07

    Benzothiazole (BTA) and its derivatives are the most important heterocyclic compounds, which are common and integral feature of a variety of natural products and pharmaceutical agents. BTA shows a variety of pharmacological properties, and its analogs offer a high degree of structural diversity that has proven useful for the search of new therapeutic agents. The broad spectrum of pharmacological activity in individual BTA derivative indicates that, this series of compounds is of an undoubted interest. The related research and developments in BTA-based medicinal chemistry have become a rapidly developing and increasingly active topic. Particularly, numerous BTA-based compounds as clinical drugs have been extensively used in practice to treat various types of diseases with high therapeutic potency. This work systematically gives a comprehensive review in current developments of BTA-based compounds in the whole range of medicinal chemistry as anticancer, antibacterial, antifungal, antiinflammatory, analgesic, anti-HIV, antioxidant, anticonvulsant, antitubercular, antidiabetic, antileishmanial, antihistaminic, antimalarial and other medicinal agents. It is believed that, this review article is helpful for new thoughts in the quest for rational designs of more active and less toxic BTA-based drugs, as well as more effective diagnostic agents and pathologic probes.

  18. Comprehensive review in current developments of imidazole-based medicinal chemistry.

    PubMed

    Zhang, Ling; Peng, Xin-Mei; Damu, Guri L V; Geng, Rong-Xia; Zhou, Cheng-He

    2014-03-01

    Imidazole ring is an important five-membered aromatic heterocycle widely present in natural products and synthetic molecules. The unique structural feature of imidazole ring with desirable electron-rich characteristic is beneficial for imidazole derivatives to readily bind with a variety of enzymes and receptors in biological systems through diverse weak interactions, thereby exhibiting broad bioactivities. The related research and developments of imidazole-based medicinal chemistry have become a rapidly developing and increasingly active topic. Particularly, numerous imidazole-based compounds as clinical drugs have been extensively used in the clinic to treat various types of diseases with high therapeutic potency, which have shown the enormous development value. This work systematically gives a comprehensive review in current developments of imidazole-based compounds in the whole range of medicinal chemistry as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents, together with their potential applications in diagnostics and pathology. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic imidazole-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes.

  19. Insights into diastereoisomeric characterization of tetrahydropyridazine amino acid derivatives: crystal structures and gas phase ion chemistry.

    PubMed

    Giorgi, Gianluca; Favi, Gianfranco; Attanasi, Orazio A

    2013-08-14

    Structural, conformational properties, and gas phase reactivity of two representative diastereoisomeric members of a series of α,α-tetrahydropyridazine amino acid derivatives have been investigated by using X-ray crystallography, tandem mass spectrometry and theoretical calculations. Both diastereoisomers show an unusual screw-boat conformation of the tetrahydropyridazine ring. While protonated molecules mainly decompose in the gas phase by loss of acetamide, the main reactivity of the [M + Na](+) species consists of loss of PhNCO followed by acetamide and it is strictly dependent upon the stereochemistry of the parent compound. The most stable energy minimized structures obtained by theoretical calculations are in full agreement with the experimental data and allowed us to rationalize the gas phase reaction pathways.

  20. Green chemistry in protected horticulture: the use of peroxyacetic acid as a sustainable strategy.

    PubMed

    Carrasco, Gilda; Urrestarazu, Miguel

    2010-05-03

    Global reduction of chemical deposition into the environment is necessary. In protected horticulture, different strategies with biodegradable products are used to control pathogens. This review presents the available tools, especially for the management of protected horticultural species, including vegetables and ornamental plants. An analysis of the potential for degradable products that control pathogens and also encourage other productive factors, such as oxygen in the root system, is presented. Biosecurity in fertigation management of protected horticulture is conducted by using peroxyacetic acid mixtures that serve three basic principles: first, the manufacture of these products does not involve polluting processes; second, they have the same function as other chemicals, and third, after use and management there is no toxic residue left in the environment. The sustainability of protected horticulture depends on the development and introduction of technologies for implementation in the field.

  1. Effects of morpholine and boric acid implementation on secondary chemistry and corrosion product transport

    SciTech Connect

    Siegwarth, D.P.; Pearl, W.L.; Sawochka, S.G.; Clouse, M.E.

    1992-07-01

    This project expanded the database on the effects of morpholine use as a pH control additive in the secondary water system of pressurized water reactors. Tests carried out at Alabama Power`s Joseph M. Farley Units 1 and 2, Northern States Power`s Prairie Island Unit 2, and Commonwealth Edison`s Byron Unit 1 demonstrated that the use of morpholine reduced corrosion product transport in PWR secondary systems by up to a factor of 2. Further reductions were achieved by eliminating copper alloy tubing and increasing secondary cycles pH. Steam generator boric acid treatment in plants with all ferrous secondary cycles operated with morpholine was shown to have a minimal effect on iron transport.

  2. Effects of morpholine and boric acid implementation on secondary chemistry and corrosion product transport

    SciTech Connect

    Siegwarth, D.P.; Pearl, W.L.; Sawochka, S.G.; Clouse, M.E. )

    1992-07-01

    This project expanded the database on the effects of morpholine use as a pH control additive in the secondary water system of pressurized water reactors. Tests carried out at Alabama Power's Joseph M. Farley Units 1 and 2, Northern States Power's Prairie Island Unit 2, and Commonwealth Edison's Byron Unit 1 demonstrated that the use of morpholine reduced corrosion product transport in PWR secondary systems by up to a factor of 2. Further reductions were achieved by eliminating copper alloy tubing and increasing secondary cycles pH. Steam generator boric acid treatment in plants with all ferrous secondary cycles operated with morpholine was shown to have a minimal effect on iron transport.

  3. Green Chemistry in Protected Horticulture: The Use of Peroxyacetic Acid as a Sustainable Strategy

    PubMed Central

    Carrasco, Gilda; Urrestarazu, Miguel

    2010-01-01

    Global reduction of chemical deposition into the environment is necessary. In protected horticulture, different strategies with biodegradable products are used to control pathogens. This review presents the available tools, especially for the management of protected horticultural species, including vegetables and ornamental plants. An analysis of the potential for degradable products that control pathogens and also encourage other productive factors, such as oxygen in the root system, is presented. Biosecurity in fertigation management of protected horticulture is conducted by using peroxyacetic acid mixtures that serve three basic principles: first, the manufacture of these products does not involve polluting processes; second, they have the same function as other chemicals, and third, after use and management there is no toxic residue left in the environment. The sustainability of protected horticulture depends on the development and introduction of technologies for implementation in the field. PMID:20559497

  4. Use of sustainable chemistry to produce an acyl amino acid surfactant.

    PubMed

    Reznik, Gabriel O; Vishwanath, Prashanth; Pynn, Michelle A; Sitnik, Joy M; Todd, Jeffrey J; Wu, Jun; Jiang, Yan; Keenan, Brendan G; Castle, Andrew B; Haskell, Richard F; Smith, Temple F; Somasundaran, Ponisseril; Jarrell, Kevin A

    2010-05-01

    Surfactants find wide commercial use as foaming agents, emulsifiers, and dispersants. Currently, surfactants are produced from petroleum, or from seed oils such as palm or coconut oil. Due to concerns with CO(2) emissions and the need to protect rainforests, there is a growing necessity to manufacture these chemicals using sustainable resources In this report, we describe the engineering of a native nonribosomal peptide synthetase pathway (i.e., surfactin synthetase), to generate a Bacillus strain that synthesizes a highly water-soluble acyl amino acid surfactant, rather than the water insoluble lipopeptide surfactin. This novel product has a lower CMC and higher water solubility than myristoyl glutamate, a commercial surfactant. This surfactant is produced by fermentation of cellulosic carbohydrate as feedstock. This method of surfactant production provides an approach to sustainable manufacturing of new surfactants.

  5. Polarity based fractionation of fulvic acids.

    PubMed

    Li, Aimin; Hu, Jundong; Li, Wenhui; Zhang, Wei; Wang, Xuejun

    2009-11-01

    Fulvic acids from the soil of Peking University (PF) and a Nordic river (NF) were separated into well defined sub-fractions using sequential elution techniques based on eluent polarity. The chemical properties of the fractions including: PF1 and NF1 (eluted by 0.01 M HCl), PF2 and NF2 (eluted by 0.01 M HCl+20% methanol), PF3 and NF3 (eluted by 0.01 M HCl+40% methanol), and PF4 and NF4 (eluted by 100% methanol), were characterized using UV-Visible spectroscopy, elemental analysis and (13)C NMR. The results showed that the UV absorptions of the elution peaks at 280 nm (A280) increased from PF2 to PF4 and NF2 to NF4. No elution peaks were observed for PF1 and NF1. The carbon contents increased from 43.34% to 51.90% and 43.06% to 53.26% while the oxygen contents decreased from 46.39% to 36.76% and 49.76% to 40.03% for PF1-PF4 and NF1-NF4, respectively. As a polarity indicator, the (O+N)/C ratio for PF1-PF4 and NF1-NF4 decreased from 0.88 to 0.62 and 0.89 to 0.58, respectively. The aromatic carbon content increased from PF1 to PF4 and NF1 to NF4, suggesting an increase of the hydrophobicity of these fractions. The polarity was positively related to the ratio of UV absorption at 250 nm and 365 nm (E2/E3), and negatively related to the aromaticity. A high positive relationship between the aromaticity and E2/E3 of fulvic acid fractions was also obtained. The use of an eluent with a decreasing polarity allowed to providing simpler fractions of soil and aquatic fulvic acids.

  6. Redox and complexation chemistry of the Cr(VI)/Cr(V)/Cr(IV)-D-glucuronic acid system.

    PubMed

    González, Juan Carlos; García, Silvia; Bellú, Sebastián; Salas Peregrín, Juan Manuel; Atria, Ana María; Sala, Luis Federico; Signorella, Sandra

    2010-03-07

    When excess uronic acid over Cr(VI) is used, the oxidation of D-glucuronic acid (Glucur) by Cr(VI) yields D-glucaric acid (Glucar) and Cr(III) as final products. The redox reaction involves the formation of intermediate Cr(IV) and Cr(V) species, with Cr(VI) and Cr(V) reacting with Glucur at comparable rates. The rate of disappearance of Cr(VI), and Cr(V) increases with [H(+)] and [substrate]. The experimental results indicated that Cr(IV) is a very reactive intermediate since its disappearance rate is much faster than Cr(VI)/Cr(V) and decreases when [H(+)] rises. Even at high [H(+)] Cr(IV) intermediate was involved in fast steps and does not accumulate in the reaction. Kinetic studies show that the redox reaction between Glucur and Cr(VI) proceeds through a mechanism combining one- and two-electron pathways for the reduction of intermediate Cr(IV) by the organic substrate: Cr(VI) --> Cr(IV) --> Cr(II) and Cr(VI) --> Cr(IV) --> Cr(III). The mechanism is supported by the observation of free radicals, CrO(2)(2+) (superoxoCr(III) ion) and Cr(V) as reaction intermediates. The EPR spectra show that five-co-ordinate oxo-Cr(V) bischelates are formed at pH < or = 4 with the uronic acid bound to Cr(V) through the carboxylate and the alpha-OH group of the furanose form. Five-co-ordinated oxo-Cr(V) monochelates are observed as minor species in addition to the major five-co-ordinated oxo-Cr(V) bischelates. At pH 7.5 the EPR spectra show the formation of a Cr(V) complex where the cis-diol groups of Glucur participate in the bonding to Cr(V). In vitro, our studies on the chemistry of Cr(V) complexes can provide information on the nature of the species that are likely to be stabilized in vivo. In particular, the EPR pattern of Glucur-Cr(V) species can be used as a finger print to identify Cr(V) complexes formed in biological systems.

  7. Manufacturing of Peptide Microarrays Based on Catalyst-Free Click Chemistry.

    PubMed

    Prim, Denis; Pfeifer, Marc E

    2016-01-01

    Immobilization of peptides to a solid surface is frequently an important first step before they can be probed with a variety of biological samples in a heterogeneous assay format for research and clinical diagnostic purposes. Peptides can be derivatized in many ways to subsequently covalently attach them to an activated solid surface such as epoxy-functionalized glass slides. Here, we describe a clean, efficient, and reproducible fabrication process based on catalyst-free click chemistry compatible with the construction of low- to high-density peptide microarrays.

  8. Impact of STS (Context-Based Type of Teaching) in Comparison with a Textbook Approach on Attitudes and Achievement in Community College Chemistry Classrooms

    ERIC Educational Resources Information Center

    Perkins, Gita

    2011-01-01

    The purpose of this study was to analyze the impact of a context-based teaching approach (STS) versus a more traditional textbook approach on the attitudes and achievement of community college chemistry students. In studying attitudes toward chemistry within this study, I used a 30-item Likert scale in order to study the importance of chemistry in…

  9. Thinking about online sources: Exploring students' epistemic cognition in internet-based chemistry learning

    NASA Astrophysics Data System (ADS)

    Dai, Ting

    This dissertation investigated the relation between epistemic cognition---epistemic aims and source beliefs---and learning outcome in an Internet--based research context. Based on a framework of epistemic cognition (Chinn, Buckland, & Samarapungavan, 2011), a context--specific epistemic aims and source beliefs questionnaire (CEASBQ) was developed and administered to 354 students from college--level introductory chemistry courses. A series of multitrait--multimethod model comparisons provided evidence for construct convergent and discriminant validity for three epistemic aims--- true beliefs, justified beliefs, explanatory connection, which were all distinguished from, yet correlated with, mastery goals. Students' epistemic aims were specific to the chemistry topics in research. Multidimensional scaling results indicated that students' source evaluation was based on two dimensions--- professional expertise and first--hand knowledge, suggesting a multidimensional structure of source beliefs. Most importantly, online learning outcome was found to be significantly associated with two epistemic aims---justified beliefs and explanatory connection: The more students sought justifications in the online research, the lower they tended to score on the learning outcome measure, whereas the more students sought explanatory connections between information, the higher they scored on the outcome measure. There was a significant but small positive association between source beliefs and learning outcome. The influences of epistemic aims and source beliefs on learning outcome were found to be above and beyond the effects of a number of covariates, including prior knowledge and perceived ability with online sources.

  10. The μ3 model of acids and bases: extending the Lewis theory to intermetallics.

    PubMed

    Stacey, Timothy E; Fredrickson, Daniel C

    2012-04-02

    A central challenge in the design of new metallic materials is the elucidation of the chemical factors underlying the structures of intermetallic compounds. Analogies to molecular bonding phenomena, such as the Zintl concept, have proven very productive in approaching this goal. In this Article, we extend a foundational concept of molecular chemistry to intermetallics: the Lewis theory of acids and bases. The connection is developed through the method of moments, as applied to DFT-calibrated Hückel calculations. We begin by illustrating that the third and fourth moments (μ(3) and μ(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. μ(3) controls the balance of states above and below the DOS minimum, with μ(4) then determining the minimum's depth. In this way, μ(3) predicts an ideal occupancy for the DOS distribution. The μ(3)-ideal electron count is used to forge a link between the reactivity of transition metals toward intermetallic phase formation, and that of Lewis acids and bases toward adduct formation. This is accomplished through a moments-based definition of acidity which classifies systems that are electron-poor relative to the μ(3)-ideal as μ(3)-acidic, and those that are electron-rich as μ(3)-basic. The reaction of μ(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the μ(3) acidity or basicity of the reactants. This μ(3)-neutralization is traced to the influence of electronegativity differences at heteroatomic contacts on the projected DOS curves of the atoms involved. The role of μ(3)-acid/base interactions in intermetallic phases is demonstrated through the examination of 23 binary phases forming between 3d metals, the stability range of the CsCl type, and structural trends within the Ti-Ni system.

  11. A graphene-based electrochemical competitive immunosensor for the sensitive detection of okadaic acid in shellfish

    NASA Astrophysics Data System (ADS)

    Eissa, Shimaa; Zourob, Mohammed

    2012-11-01

    A novel graphene-based voltammetric immunosensor for sensitive detection of okadaic acid (OA) was developed. A simple and efficient electrografting method was utilized to functionalize graphene-modified screen-printed carbon electrodes (GSPE) by the electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt in acidic aqueous solution. Next, the okadaic acid antibody was covalently immobilized on the carboxyphenyl modified graphene electrodes via carbodiimide chemistry. Square wave voltammetry (SWV) was used to investigate the stepwise assembly of the immunosensor. A competitive assay between OA and a fixed concentration of okadaic acid-ovalbumin conjugate (OA-OVA) for the immobilized antibodies was employed for the detection of okadaic acid. The decrease of the [Fe(CN)6]3-/4- reduction peak current in the square wave voltammetry for various concentrations of okadaic acid was used for establishing the calibration curve. A linear relationship between the SWV peak current difference and OA concentration was obtained up to ~5000 ng L-1. The developed immunosensor allowed a detection limit of 19 ng L-1 of OA in PBS buffer. The matrix effect studied with spiked shellfish tissue extracts showed a good percentage of recovery and the method was also validated with certified reference mussel samples.A novel graphene-based voltammetric immunosensor for sensitive detection of okadaic acid (OA) was developed. A simple and efficient electrografting method was utilized to functionalize graphene-modified screen-printed carbon electrodes (GSPE) by the electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt in acidic aqueous solution. Next, the okadaic acid antibody was covalently immobilized on the carboxyphenyl modified graphene electrodes via carbodiimide chemistry. Square wave voltammetry (SWV) was used to investigate the stepwise assembly of the immunosensor. A competitive assay between OA and a fixed concentration of okadaic acid

  12. 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.

  13. Teaching biochemistry to medical students in Singapore--from organic chemistry to problem-based learning.

    PubMed

    Khoo, H E

    2005-07-01

    The medical faculty in the National University of Singapore started in 1905 but the Chair in Biochemistry was only established in 1927. For many years the biochemistry course consisted of the teaching of the organic chemistry of substances of physiological importance, nutrition, metabolism and hormones. In 1961, clinical biochemistry was introduced and in the 1980s, genetics and molecular biology were included. By then, most of the organic chemistry content had been removed as greater emphasis was placed on clinical correlation. Laboratory classes consisted of mock glucose tolerance tests and the measurement of various enzymes. By the 1990s, students were no longer interested in such practical classes, so a bold decision was made around 1995 to remove laboratory classes from the curriculum. Unfortunately, this meant that the medical students who might have been interested in laboratory work could no longer do such work. However, the new curriculum in 1999 gave the department an opportunity to offer a laboratory course as an elective for interested students. This new curriculum adopted an integrated approach with Genetics being taught as part of Paediatrics, and a new module (Structural and Cell Biology) comprising aspects of cell biology and biochemistry was introduced. This module is currently taught by staff from Anatomy, Physiology and Biochemistry. Some biochemistry content is now incorporated into the clinical problem scenarios of problem-based learning such as jaundice, diabetes mellitus, anorexia nervosa, etc. So the evolution of teaching biochemistry to medical students in Singapore has paralleled worldwide trends and moved from the didactic teaching of organic chemistry of biomolecules to problem-based learning using clinical cases.

  14. Crystal Chemistry of the Potassium and Rubidium Uranyl Borate Families Derived from Boric Acid Fluxes

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-07-19

    The reaction of uranyl nitrate with a large excess of molten boric acid in the presence of potassium or rubidium nitrate results in the formation of three new potassium uranyl borates, K{sub 2}[(UO{sub 2}){sub 2}B{sub 12}O{sub 19}(OH){sub 4}]·0.3H{sub 2}O (KUBO-1), K[(UO{sub 2}){sub 2}B{sub 10}O{sub 15}(OH){sub 5}] (KUBO-2), and K[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]·0.7H{sub 2}O (KUBO-3) and two new rubidium uranyl borates Rb{sub 2}[(UO{sub 2}){sub 2}B{sub 13}O{sub 20}(OH){sub 5}] (RbUBO-1) and Rb[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]·0.7H{sub 2}O (RbUBO-2). The latter is isotypic with KUBO-3. These compounds share a common structural motif consisting of a linear uranyl, UO{sub 2}{sup 2+}, cation surrounded by BO{sub 3} triangles and BO{sub 4} tetrahedra to create an UO{sub 8} hexagonal bipyramidal environment around uranium. The borate anions bridge between uranyl units to create sheets. Additional BO{sub 3} triangles extend from the polyborate layers and are directed approximately perpendicular to the sheets. All of these compounds adopt layered structures. With the exception of KUBO-1, the structures are all centrosymmetric. All of these compounds fluoresce when irradiated with long-wavelength UV light. The fluorescence spectrum yields well-defined vibronically coupled charge-transfer features.

  15. Coordination chemistry of the soft chiral Lewis acid [Cp*Ir(TsDPEN)]+.

    PubMed

    Letko, Christopher S; Heiden, Zachariah M; Rauchfuss, Thomas B; Wilson, Scott R

    2011-06-20

    The paper surveys the binding of anions to the unsaturated 16e Lewis acid [Cp*Ir(TsDPEN)](+) ([1H](+)), where TsDPEN is racemic H(2)NCHPhCHPhNTs(-). The derivatives Cp*IrX(TsDPEN) were characterized crystallographically for X(-) = CN(-), Me(C═NH)S(-), NO(2)(-), 2-pyridonate, and 0.5 MoS(4)(2-). [(1H)(2)(μ-CN)](+) forms from [1H](+) and 1H(CN). Aside from 2-pyridone, amides generally add reversibly and bind to Ir through N. Thioacetamide binds irreversibly through sulfur. Compounds of the type Cp*IrX(TsDPEN) generally form diastereoselectively, although diastereomeric products were observed for the strong ligands (X = CN(-), H(-) (introduced via BH(4)(-)), or Me(C═NH)S(-)). Related experiments on the reaction (p-cymene)Ru(TsDPEN-H) + BH(4)(-) gave two diastereomers of (p-cymene)RuH(TsDPEN), the known hydrogenation catalyst and a second isomer that hydrogenated acetophenone more slowly. These experiment provide new insights into the enantioselectivity of these catalysts. Diastereomerization in all cases was first order in metal with modest solvent effects. The diphenyl groups are generally diequatorial for the stable diastereomers. For the 2-pyridonate adduct, axial phenyl groups are stabilized in the solid state by puckering of the IrN(2)C(2) ring induced by intramolecular hydrogen-bonding. Crystallographic analysis of [Cp*Ir(TsDPEN)](2)(MoS(4)) revealed a unique example of a κ(1),κ(1)-tetrathiometallate ligand. Cp*Ir(SC(NH)Me)TsDPEN) is the first example of a κ(1)-S-thioamidato complex.

  16. The 2005 catastrophic acid crater lake drainage, lahar, and acidic aerosol formation at Mount Chiginagak volcano, Alaska, USA: Field observations and preliminary water and vegetation chemistry results

    NASA Astrophysics Data System (ADS)

    Schaefer, Janet R.; Scott, William E.; Evans, William C.; Jorgenson, Janet; McGimsey, Robert G.; Wang, Bronwen

    2008-07-01

    A mass of snow and ice 400-m-wide and 105-m-thick began melting in the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably owing to increased heat flux from the hydrothermal system, or possibly from magma intrusion and degassing. In early May 2005, an estimated 3.8 × 106 m3 of sulfurous, clay-rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km3 in volume at a pH of 2.9 to 3.1), killing all aquatic life, and preventing the annual salmon run. Over 2 months later, crater lake water sampled 8 km downstream of the outlet after considerable dilution from glacial meltwater was a weak sulfuric acid solution (pH = 3.2, SO4 = 504 mg/L, Cl = 53.6 mg/L, and F = 7.92 mg/L). The acid flood waters caused severe vegetation damage, including plant death and leaf kill along the flood path. The crater lake drainage was accompanied by an ambioructic flow of acidic aerosols that followed the flood path, contributing to defoliation and necrotic leaf damage to vegetation in a 29 km2 area along and above affected streams, in areas to heights of over 150 m above stream level. Moss species killed in the event contained high levels of sulfur, indicating extremely elevated atmospheric sulfur content. The most abundant airborne phytotoxic constituent was likely sulfuric acid aerosols that were generated during the catastrophic partial crater lake drainage event. Two mechanisms of acidic aerosol formation are proposed: (1) generation of aerosol mist through turbulent flow of acidic water and (2) catastrophic gas exsolution. This previously undocumented phenomenon of simultaneous vegetation-damaging acidic aerosols accompanying drainage of an acidic

  17. The 2005 catastrophic acid crater lake drainage, lahar, and acidic aerosol formation at Mount Chiginagak volcano, Alaska, USA: Field observations and preliminary water and vegetation chemistry results

    USGS Publications Warehouse

    Schaefer, J.R.; Scott, W.E.; Evans, William C.; Jorgenson, J.; McGimsey, R.G.; Wang, B.

    2008-01-01

    A mass of snow and ice 400-m-wide and 105-m-thick began melting in the summit crater of Mount Chiginagak volcano sometime between November 2004 and early May 2005, presumably owing to increased heat flux from the hydrothermal system, or possibly from magma intrusion and degassing. In early May 2005, an estimated 3.8??106 m3 of sulfurous, clay-rich debris and acidic water, with an accompanying acidic aerosol component, exited the crater through a tunnel at the base of a glacier that breaches the south crater rim. Over 27 km downstream, the acidic waters of the flood inundated an important salmon spawning drainage, acidifying Mother Goose Lake from surface to depth (approximately 0.5 km3 in volume at a pH of 2.9 to 3.1), killing all aquatic life, and preventing the annual salmon run. Over 2 months later, crater lake water sampled 8 km downstream of the outlet after considerable dilution from glacial meltwater was a weak sulfuric acid solution (pH = 3.2, SO4 = 504 mg/L, Cl = 53.6 mg/L, and F = 7.92 mg/L). The acid flood waters caused severe vegetation damage, including plant death and leaf kill along the flood path. The crater lake drainage was accompanied by an ambioructic flow of acidic aerosols that followed the flood path, contributing to defoliation and necrotic leaf damage to vegetation in a 29 km2 area along and above affected streams, in areas to heights of over 150 m above stream level. Moss species killed in the event contained high levels of sulfur, indicating extremely elevated atmospheric sulfurcontent. The most abundant airborne phytotoxic constituent was likely sulfuric acid aerosols that were generated during the catastrophic partial crater lake drainage event. Two mechanisms of acidic aerosol formation are proposed: (1) generation of aerosol mist through turbulent flow of acidic water and (2) catastrophic gas exsolution. This previously undocumented phenomenon of simultaneous vegetationdamaging acidic aerosols accompanying drainage of an acidic crater

  18. Pre-Nursing Students Perceptions of Traditional and Inquiry Based Chemistry Laboratories

    NASA Astrophysics Data System (ADS)

    Rogers, Jessica

    This paper describes a process that attempted to meet the needs of undergraduate students in a pre-nursing chemistry class. The laboratory was taught in traditional verification style and students were surveyed to assess their perceptions of the educational goals of the laboratory. A literature review resulted in an inquiry based method and analysis of the needs of nurses resulted in more application based activities. This new inquiry format was implemented the next semester, the students were surveyed at the end of the semester and results were compared to the previous method. Student and instructor response to the change in format was positive. Students in the traditional format placed goals concerning technique above critical thinking and felt the lab was easy to understand and carry out. Students in the inquiry based lab felt they learned more critical thinking skills and enjoyed the independence of designing experiments and answering their own questions.

  19. A new liquid chromatography-mass spectrometry-based strategy to integrate chemistry, morphology, and evolution of eggplant (Solanum) species.

    PubMed

    Wu, Shi-Biao; Meyer, Rachel S; Whitaker, Bruce D; Litt, Amy; Kennelly, Edward J

    2013-11-01

    This study presents a strategy based on repeatable reversed-phase LC-TOF-MS methods and statistical tools, including untargeted PCA and targeted PLS/OPLS-DA models, to analyze 31 accessions representing 24 species in the eggplant genus Solanum (Solanaceae), including eight species whose metabolic profiles were studied for the first time. Sixty-two Solanum metabolites were identified after detailed analysis of UV absorbance spectra, mass spectral fragmentation patterns, NMR spectra, and/or co-injection experiments with authentic standards. Among these were two new 5-O-caffeoylquinic acid derivatives that were identified by analyzing their MS/MS fragmentation. Based on these results, a Solanum metabolic database (SMD) and a detailed biosynthetic pathway of Solanum metabolites were created. Results of analyses identified seven marker metabolites that distinguish four Solanum sections, and revealed species-specific chemical patterns. Combining LC-MS data with multivariate statistical analysis was proven effective in studying the metabolic network within the large genus Solanum, allowing for integration of complicated chemistry, morphology, and evolutionary relationships.

  20. Acid precipitation studies in Colorado and Wyoming: interim report of surveys of montane amphibians and water chemistry

    USGS Publications Warehouse

    Corn, Paul Stephen; Stolzenburg, William; Bury, R. Bruce

    1989-01-01

    Acid deposition may be detrimental or stressful to native populations of wildlife. Because many species of amphibians breed in shallow ponds created by spring rains or melting snow, they may be particularly vulnerable to the effects of acidification. From 1986 to 1988, we surveyed 105 locations in the central Rocky Mountains where amphibians had been recorded previously, and we found that two species of amphibians had experiences major losses. We found the northern leopard frog (Rana pipiens) at only 4 of 33 (12%) historically known localities, and the boreal toad (Bufo boreas) was present at 10 of 59 (17%) known localities. Three other species have not suffered region-wide declines. Tiger salamanders (Ambystoma tigrinum) and wood frogs (Rana sylvatica) were present at 45% and 69% of known localities respectively, and were observed at several localities were they had not been recorded previously. Chorus frogs (Pseudacris triseriata) suffered a catastrophic decline in population size in one population monitored since 1961, but regionally, this species was observed in 36 of 56 (64%) known localities and in another 19 localities where there were no previous records. Complete water chemistry was recorded for 41 localities, and pH was measured at 110 sites in total. Acid neutralizing capacity, pH, specific conductivity, and cation concentrations were negatively correlated with elevation. However, in mountain ponds and lakes, pH was rarely less than 6.0 during the amphibian breeding season. We tested the tolerance of embryos of the four species of frogs to low pH. The LC50 pH was 4.8 for chorus frogs, 4.4-4.7 for leopard frogs, 4.4-4.5 for boreal toads, and 4.2-4.3 for wood frogs. Survival of wood frog embryos declined when exposed to aluminum concentrations of 100 µg/L or greater, but boreal toad embryos survived exposure to aluminum concentrations of 400 µg/L. Acid deposition does not appear to be a major factor in the decline of leopard frogs and boreal toads

  1. Treatment of Electronic Energy Level Transition and Ionization Following the Particle-Based Chemistry Model

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark

    2010-01-01

    A new method of treating electronic energy level transitions as well as linking ionization to electronic energy levels is proposed following the particle-based chemistry model of Bird. Although the use of electronic energy levels and ionization reactions in DSMC are not new ideas, the current method of selecting what level to transition to, how to reproduce transition rates, and the linking of the electronic energy levels to ionization are, to the author s knowledge, novel concepts. The resulting equilibrium temperatures are shown to remain constant, and the electronic energy level distributions are shown to reproduce the Boltzmann distribution. The electronic energy level transition rates and ionization rates due to electron impacts are shown to reproduce theoretical and measured rates. The rates due to heavy particle impacts, while not as favorable as the electron impact rates, compare favorably to values from the literature. Thus, these new extensions to the particle-based chemistry model of Bird provide an accurate method for predicting electronic energy level transition and ionization rates in gases.

  2. Wastewater treatment using hybrid treatment schemes based on cavitation and Fenton chemistry: a review.

    PubMed

    Bagal, Manisha V; Gogate, Parag R

    2014-01-01

    Advanced oxidation processes such as cavitation and Fenton chemistry have shown considerable promise for wastewater treatment applications due to the ease of operation and simple reactor design. In this review, hybrid methods based on cavitation coupled with Fenton process for the treatment of wastewater have been discussed. The basics of individual processes (Acoustic cavitation, Hydrodynamic cavitation, Fenton chemistry) have been discussed initially highlighting the need for combined processes. The different types of reactors used for the combined processes have been discussed with some recommendations for large scale operation. The effects of important operating parameters such as solution temperature, initial pH, initial pollutant concentration and Fenton's reagent dosage have been discussed with guidelines for selection of optimum parameters. The optimization of power density is necessary for ultrasonic processes (US) and combined processes (US/Fenton) whereas the inlet pressure needs to be optimized in the case of Hydrodynamic cavitation (HC) based processes. An overview of different pollutants degraded under optimized conditions using HC/Fenton and US/Fenton process with comparison with individual processes have been presented. It has been observed that the main mechanism for the synergy of the combined process depends on the generation of additional hydroxyl radicals and its proper utilization for the degradation of the pollutant, which is strongly dependent on the loading of hydrogen peroxide. Overall, efficient wastewater treatment with high degree of energy efficiency can be achieved using combined process operating under optimized conditions, as compared to the individual process.

  3. Chemistry-based functional proteomics to identify novel deubiquitylating enzymes involved in viral infection.

    PubMed

    Lei, Yunlong; Xie, Ke; Huang, Kai; Wu, Hong; Huang, Canhua

    2012-05-01

    Ubiquitylation is a reversible post-translational modification pathway that regulates a variety of cellular processes including protein degradation and trafficking, intracellular localization, DNA repair, immune response and cellcycle progression. Deubiquitylating enzymes (DUBs) can remove the ubiquitin from the modified proteins and reverse the ubiquitylation-induced biological processes; hence it isn't hard to understand that viral pathogens take advantage of the host cell ubiquitin system through disturbing DUBs, for infection and replication. Although accumulated virus-related DUBs have been defined, but how viruses regulate their expression and activities is poor understand because of limitation of technologies. Recently, chemistry-based functional proteomics, which can not only monitor the alteration of abundance but also changes in activity of enzymes, was used to study the function of DUBs involved in virus infection and held much promise. Theses works suggest that chemistry-based functional proteomics is a potent strategy for high throughput screening of virus-related DUBs and exploring their roles in virus infection.

  4. Chemical tumor-targeting of nanoparticles based on metabolic glycoengineering and click chemistry.

    PubMed

    Lee, Sangmin; Koo, Heebeom; Na, Jin Hee; Han, Seung Jin; Min, Hyun Su; Lee, So Jin; Kim, Sun Hwa; Yun, Seok Hyun; Jeong, Seo Young; Kwon, Ick Chan; Choi, Kuiwon; Kim, Kwangmeyung

    2014-03-25

    Tumor-targeting strategies for nanoparticles have been predominantly based on optimization of physical properties or conjugation with biological ligands. However, their tumor-targeting abilities remain limited and insufficient. Furthermore, traditional biological binding molecules have intrinsic limitations originating from the limited amount of cellular receptors and the heterogeneity of tumor cells. Our two-step in vivo tumor-targeting strategy for nanoparticles is based on metabolic glycoengineering and click chemistry. First, an intravenous injection of precursor-loaded glycol chitosan nanoparticles generates azide groups on tumor tissue specifically by the enhanced permeation and retention (EPR) effect followed by metabolic glycoengineering. These 'receptor-like' chemical groups then enhance the tumor-targeting ability of drug-containing nanoparticles by copper-free click chemistry in vivo during a second intravenous injection. The advantage of this protocol over traditional binding molecules is that there are significantly more binding molecules on the surface of most tumor cells regardless of cell type. The subsequent enhanced tumor-targeting ability can significantly enhance the cancer therapeutic efficacy in animal studies.

  5. The successful merger of theoretical thermochemistry with fragment-based methods in quantum chemistry.

    PubMed

    Ramabhadran, Raghunath O; Raghavachari, Krishnan

    2014-12-16

    CONSPECTUS: Quantum chemistry and electronic structure theory have proven to be essential tools to the experimental chemist, in terms of both a priori predictions that pave the way for designing new experiments and rationalizing experimental observations a posteriori. Translating the well-established success of electronic structure theory in obtaining the structures and energies of small chemical systems to increasingly larger molecules is an exciting and ongoing central theme of research in quantum chemistry. However, the prohibitive computational scaling of highly accurate ab initio electronic structure methods poses a fundamental challenge to this research endeavor. This scenario necessitates an indirect fragment-based approach wherein a large molecule is divided into small fragments and is subsequently reassembled to compute its energy accurately. In our quest to further reduce the computational expense associated with the fragment-based methods and overall enhance the applicability of electronic structure methods to large molecules, we realized that the broad ideas involved in a different area, theoretical thermochemistry, are transferable to the area of fragment-based methods. This Account focuses on the effective merger of these two disparate frontiers in quantum chemistry and how new concepts inspired by theoretical thermochemistry significantly reduce the total number of electronic structure calculations needed to be performed as part of a fragment-based method without any appreciable loss of accuracy. Throughout, the generalized connectivity based hierarchy (CBH), which we developed to solve a long-standing problem in theoretical thermochemistry, serves as the linchpin in this merger. The accuracy of our method is based on two strong foundations: (a) the apt utilization of systematic and sophisticated error-canceling schemes via CBH that result in an optimal cutting scheme at any given level of fragmentation and (b) the use of a less expensive second

  6. Towards "Bildung"-Oriented Chemistry Education

    ERIC Educational Resources Information Center

    Sjöström, Jesper

    2013-01-01

    This paper concerns "Bildung"-oriented chemistry education, based on a reflective and critical discourse of chemistry. It is contrasted with the dominant type of chemistry education, based on the mainstream discourse of chemistry. "Bildung"-oriented chemistry education includes not only content knowledge in chemistry, but also…

  7. The Living Textbook of Nuclear Chemistry: A Peer-Reviewed, Web-Based, Education Resource

    ERIC Educational Resources Information Center

    Loveland, W.; Gallant, A.; Joiner, C.

    2004-01-01

    The recent developments in nuclear chemistry education are presented and an attempt is made to collect supplemental materials relating to the study and practice of nuclear chemistry. The Living Textbook of Nuclear Chemistry functions as an authoritative Web site with supplemental material for teaching nuclear and radiochemistry.

  8. Chemistry of micas and chlorite in Proterozoic acid metavolcanics and associated rocks from the Hästefält area, Norberg ore district, central Sweden

    NASA Astrophysics Data System (ADS)

    Aldahan, A. A.; Ounchanum, P.; Morad, S.

    1988-09-01

    Microprobe analyses are performed on micas (biotite, muscovite and phlogopite) and chlorite from 1.9 1.8 Ga acid K- or Na-rich metavolcanics, cordierit-emica schists and manganiferous rocks from the Hästefält area in central Sweden. The results indicate that Fe-rich biotites and muscovites containing ≥10 to ≤25% celadonite and/or pyrophyllite are common in the K- and Na-rich metavolcanics. In the cordierite-mica schists the biotites are Mg-rich and the muscovites contain less than 10% celadonite and/or pyrophyllite. The predominant mica in the manganiferous rocks are phlogopite and less frequent rather pure muscovite. The chlorites show a wide range in composition, but principally those occurring in the K- and Na-rich metavolcanics are brunsvigite and diabantite and those in the cordierite-mica schists and the manganiferous rocks are mainly sheridanite and clinochlore. The chlorites of the manganiferous rocks show enrichment in Mn compared to those in other rock types. In general the compositional variations in the micas and less commonly chlorites are strongly controlled by rock type and fluid chemistry, particularly with respect to the ratio of FeO/(FeO+MgO). Estimates of maximum prograde metamorphic temperature, based on phyllosilicates and co-existing cordierite and garnets, indicate a value of up to 500° C.

  9. Acid-base bifunctional catalytic surfaces for nucleophilic addition reactions.

    PubMed

    Motokura, Ken; Tada, Mizuki; Iwasawa, Yasuhiro

    2008-09-01

    This article illustrates the modification of oxide surfaces with organic amine functional groups to create acid-base bifunctional catalysts, summarizing our previous reports and also presenting new data. Immobilization of organic amines as bases on inorganic solid-acid surfaces afforded highly active acid-base bifunctional catalysts, which enabled various organic transformations including C--C coupling reactions, though these reactions did not proceed with either the homogeneous amine precursors or the acidic supports alone. Spectroscopic characterization, such as by solid-state MAS NMR and FTIR, revealed not only the interactions between acidic and basic sites but also bifunctional catalytic reaction mechanisms.

  10. Acid Rain Materials for Classroom Use.

    ERIC Educational Resources Information Center

    Factor, Lance; Kooser, Robert G.

    This booklet contains three separate papers suitable for use in an advanced high school or college chemistry course. The first paper provides background information on acids and bases. The second paper provides additional background information, focusing on certain aspects of atmospheric chemistry as it relates to the acid rain problem. An attempt…

  11. Thermochemical comparisons of homogeneous and heterogeneous acids and bases. 1. Sulfonic acid solutions and resins as prototype Broensted acids

    SciTech Connect

    Arnett, E.M.; Haaksma, R.A.; Chawla, B.; Healy, M.H.

    1986-08-06

    Heats of ionization by thermometric titration for a series of bases (or acids) can be used to compare solid acids (or bases) with liquid analogues bearing the same functionalities in homogeneous solutions. The method is demonstrated for Broensted acids by reacting a series of substituted nitrogen bases with solutions of p-toluenesulfonic acid (PTSA) in acetonitrile and with suspensions of the microporous polymeric arylsulfonic acid resin-Dowex 50W-X8 in the same solvent. Under well-controlled anhydrous conditions there is a good correlation (r = 0.992) between the heats of reaction of the bases with the homogeneous and heterogeneous acid systems, but the homogeneous system gives a more exothermic interaction by 3-4 kcal mol/sup -1/ for a series of 29 substituted pyrimidines, anilines, and some other amines. This difference may be attributed to homohydrogen bonding interactions between excess acid and sulfonate anion sites which are more restricted geometrically in the resin than in solution. Other factors which affect the enthalpy change for the acid-base interaction are the acid/base ratio, the water content of the sulfonic acid, the solvent, and the resin structure (e.g., microporous vs. macroporous). Steric hindrance in the base does not differentiate solid from homogeneous acid. In addition to the use of titration calorimetry, heats of immersion are reported for the Dowex-arylsulfonic acid resins and the Nafion-perfluorinated sulfonic acid resin in a series of basic liquids. The results are compared with each other and with those from a previous study of several varieties of coal.

  12. A Study on Advanced Lithium-Based Battery Cell Chemistries to Enhance Lunar Exploration Missions

    NASA Technical Reports Server (NTRS)

    Reid, Concha; Bennett, William

    2009-01-01

    NASA's Exploration Technology Development Program (ETDP) Energy Storage Project conducted an advanced lithium-based battery chemistry feasibility study to determine the best advanced chemistry to develop for the Altair lunar lander and the Extravehicular Activities (EVA) advanced lunar surface spacesuit. These customers require safe, reliable energy storage systems with extremely high specific energy as compared to today's state-of-the-art batteries. Based on customer requirements, the specific energy goals for the development project are 220 watt-hours per kilogram (Wh/kg) delivered at the battery level at 0 degrees Celsius (degrees Celcius) at a C/10 discharge rate. Continuous discharge rates between C/5 and C/2, operation over 0 to 30 degrees C, and 200 cycles are targeted. The team, consisting of members from NASA Glenn Research Center, Johnson Space Center, and Jet Propulsion laboratory, surveyed the literature, compiled information on recent materials developments, and consulted with other battery experts in the community to identify advanced battery materials that might be capable of achieving the desired results with further development. A variety of electrode materials were considered, including layered metal oxides, spinel oxides, and olivine-type cathode materials, and lithium metal, lithium alloy, and silicon-based composite anode materials. lithium-sulfur systems were also considered. Hypothetical cell constructs that combined compatible anode and cathode materials with suitable electrolytes, separators, current collectors, headers, and cell enclosures were modeled. While some of these advanced materials are projected to obtain the desired electrical performance, there are risks that also factored into the decision making process. The risks include uncertainties due to issues such as safety of a system containing some of these materials, ease of scaling-up of large batches of raw materials, adaptability of the materials to processing using established

  13. 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.

  14. Acid-Base Behavior in Hydrothermal Processing of Wastes - Final Report

    SciTech Connect

    Johnston, K.; Rossky, P.

    2000-12-01

    A major obstacle to development of hydrothermal oxidation technology has been a lack of scientific knowledge of chemistry in hydrothermal solution above 350 C, particularly acid-base behavior, and transport phenomena, which is needed to understand corrosion, metal-ion complexation, and salt precipitation and recovery. Our objective has been to provide this knowledge with in situ UV-visible spectroscopic measurements and fully molecular computer simulation. Our recent development of relatively stable organic UV-visible pH indicators for supercritical water oxidation offers the opportunity to characterize buffers and to monitor acid-base titrations. These results have important implications for understanding reaction pathways and yields for decomposition of wastes in supercritical water.

  15. Chemistry around imidazopyrazine and ibuprofen: discovery of novel fatty acid amide hydrolase (FAAH) inhibitors.

    PubMed

    De Wael, Frédéric; Muccioli, Giulio G; Lambert, Didier M; Sergent, Thérèse; Schneider, Yves-Jacques; Rees, Jean-François; Marchand-Brynaert, Jacqueline

    2010-09-01

    Based on the imidazo-[1,2-a]-pyrazin-3-(7H)-one scaffold, a dual action prodrug has been designed for combining antioxidant and anti-inflammatory activities, possibly unmasked upon oxidation. The construction of the target-molecule requires two building blocks, namely a 2-amino-1,4-pyrazine and a 2-ketoaldehyde. Attempts to synthesize the 2-ketoaldehyde (5a) derived from ibuprofen failed, but led to the corresponding 2-ketoaldoxime (7a) which could not be condensed with the pyrazine synthons. However, a model compound, i.e. phenylglyoxal aldoxime, reacted well under microwave activation to furnish novel imidazo[1,2-a]-pyrazine-3-(7H)-imine derivatives (18a,b). These heterobicycles behave as antioxidants by inhibiting the lipid peroxidation, and one compound (18b) is endowed with a significant anti-inflammatory effect in a cellular test. Unexpectedly, all the synthetic intermediates derived from ibuprofen are good inhibitors of FAAH, the most active compound (4a) featuring the 1,3-dithian-2-yl motif.

  16. Calcium-based multi-element chemistry for grid-scale electrochemical energy storage

    NASA Astrophysics Data System (ADS)

    Ouchi, Takanari; Kim, Hojong; Spatocco, Brian L.; Sadoway, Donald R.

    2016-03-01

    Calcium is an attractive material for the negative electrode in a rechargeable battery due to its low electronegativity (high cell voltage), double valence, earth abundance and low cost; however, the use of calcium has historically eluded researchers due to its high melting temperature, high reactivity and unfavorably high solubility in molten salts. Here we demonstrate a long-cycle-life calcium-metal-based rechargeable battery for grid-scale energy storage. By deploying a multi-cation binary electrolyte in concert with an alloyed negative electrode, calcium solubility in the electrolyte is suppressed and operating temperature is reduced. These chemical mitigation strategies also engage another element in energy storage reactions resulting in a multi-element battery. These initial results demonstrate how the synergistic effects of deploying multiple chemical mitigation strategies coupled with the relaxation of the requirement of a single itinerant ion can unlock calcium-based chemistries and produce a battery with enhanced performance.

  17. The multiple roles of computational chemistry in fragment-based drug design

    NASA Astrophysics Data System (ADS)

    Law, Richard; Barker, Oliver; Barker, John J.; Hesterkamp, Thomas; Godemann, Robert; Andersen, Ole; Fryatt, Tara; Courtney, Steve; Hallett, Dave; Whittaker, Mark

    2009-08-01

    Fragment-based drug discovery (FBDD) represents a change in strategy from the screening of molecules with higher molecular weights and physical properties more akin to fully drug-like compounds, to the screening of smaller, less complex molecules. This is because it has been recognised that fragment hit molecules can be efficiently grown and optimised into leads, particularly after the binding mode to the target protein has been first determined by 3D structural elucidation, e.g. by NMR or X-ray crystallography. Several studies have shown that medicinal chemistry optimisation of an already drug-like hit or lead compound can result in a final compound with too high molecular weight and lipophilicity. The evolution of a lower molecular weight fragment hit therefore represents an attractive alternative approach to optimisation as it allows better control of compound properties. Computational chemistry can play an important role both prior to a fragment screen, in producing a target focussed fragment library, and post-screening in the evolution of a drug-like molecule from a fragment hit, both with and without the available fragment-target co-complex structure. We will review many of the current developments in the area and illustrate with some recent examples from successful FBDD discovery projects that we have conducted.

  18. The multiple roles of computational chemistry in fragment-based drug design.

    PubMed

    Law, Richard; Barker, Oliver; Barker, John J; Hesterkamp, Thomas; Godemann, Robert; Andersen, Ole; Fryatt, Tara; Courtney, Steve; Hallett, Dave; Whittaker, Mark

    2009-08-01

    Fragment-based drug discovery (FBDD) represents a change in strategy from the screening of molecules with higher molecular weights and physical properties more akin to fully drug-like compounds, to the screening of smaller, less complex molecules. This is because it has been recognised that fragment hit molecules can be efficiently grown and optimised into leads, particularly after the binding mode to the target protein has been first determined by 3D structural elucidation, e.g. by NMR or X-ray crystallography. Several studies have shown that medicinal chemistry optimisation of an already drug-like hit or lead compound can result in a final compound with too high molecular weight and lipophilicity. The evolution of a lower molecular weight fragment hit therefore represents an attractive alternative approach to optimisation as it allows better control of compound properties. Computational chemistry can play an important role both prior to a fragment screen, in producing a target focussed fragment library, and post-screening in the evolution of a drug-like molecule from a fragment hit, both with and without the available fragment-target co-complex structure. We will review many of the current developments in the area and illustrate with some recent examples from successful FBDD discovery projects that we have conducted.

  19. Eutrophication of Lake Wingra: A Chemistry-Based Environmental Science Module

    NASA Astrophysics Data System (ADS)

    Howe, Ann C.; Cizmas, Leslie; Bereman, Robert

    1999-07-01

    The paper describes the development and field test of a curriculum module for introductory chemistry by an interinstitutional, interdisciplinary team representing the disciplines of chemistry, biology, political science, environmental management and computer visualization. The module was designed to show that a serious and common worldwide environmental problem, the eutrophication of freshwater lakes, is directly related to the chemical reactions of phosphates. The module, which includes a student manual, an instructor's manual, and a computer visualization component, is based on a case study of Lake Wingra in Madison, Wisconsin. The module was field tested at two sites, after which 80% of students gave it a high overall rating. Attitude questionnaires administered before and after the unit was taught showed that students increased their interest in environmental problems, increased their understanding of the complexity of the problems, and had a higher level of personal commitment to address environmental problems. With changes in emphasis the module is suitable for use in other courses, including economics, biological science, and environmental science.

  20. Dissolution of beidellite in acidic solutions: Ion exchange reactions and effect of crystal chemistry on smectite reactivity

    NASA Astrophysics Data System (ADS)

    Robin, Valentin; Tertre, Emmanuel; Regnault, Olivier; Descostes, Michael

    2016-05-01

    The dissolution rate of beidellite, a dioctahedral smectite with tetrahedral charge that is a common swelling clay mineral in surface and subsurface natural environments, was studied in acidic solutions at 25 °C under far from equilibrium conditions. A <0.3 μm size fraction of SBId1 beidellite ((Si7.148Al0.852)(Al3.624Mg0.18Fe(III)0.224)O20(OH)4M+0.948) purchased from the Clay Mineral Society was used as the starting material, and experiments were performed in stirred flow-through reactors using HCl solutions with pH values ranging from 1 to 3. Several hydrodynamic conditions were tested using different flow rates with stirred and non-stirred particles. The aqueous Al/Si ratio measured at the outlet of the reactor was followed as a function of time and compared to solid stoichiometry values to assess the mechanisms occurring at the solid/solution interface. The reversible adsorption of Al3+ in the smectite interlayer space was evidenced for pH > 1.1, and the presence of an amorphous Si-enriched layer can be reasonably assumed in some cases from the interpretation of the aqueous concentrations and the characterization of the solid phase (X-ray diffraction and FTIR spectroscopy). Beidellite dissolution rates normalized to the sample mass (mol g-1 s-1) were obtained from Si and Al concentrations under steady state dissolution conditions. Calculated rates were compared with those previously reported for montmorillonite in several publications. The beidellite dissolution rates are, on average, ten times lower than those of montmorillonite. This implies that the smectite crystal chemistry (i.e., amount of Al3+ versus Mg2+ or Fe3+ substitution in the structure) has a strong effect on its stability and should be considered in reactive transport models in which the dissolution properties of smectites are taken into account.

  1. Heterogeneous Chemistry of Individual Mineral Dust Particles with Nitric Acid. A Combined CCSEM/EDX, ESEM AND ICP-MS Study

    SciTech Connect

    Laskin, Alexander; Wietsma, Thomas W.; Krueger, Brenda J.; Grassian, Vicki H.

    2005-05-26

    The heterogeneous chemistry of individual dust particles from four authentic dust samples with gas-phase nitric acid was investigated in this study. Morphology and compositional changes of individual particles as they react with nitric acid were observed using conventional scanning electron microscopy with energy dispersive analysis of X-rays (SEM/EDX) and computer controlled SEM/EDX. Environmental Scanning Electron Microscopy (ESEM) was utilized to investigate the hygroscopic behavior of mineral dust particles reacted with nitric acid. Differences in the reactivity of mineral dust particles from these four different dust source regions with nitric acid were observed. Mineral dust from source regions containing high levels of calcium, namely China loess dust and Saudi coastal dust, were found to react to the greatest extent.

  2. Computational Materials Science and Chemistry: Accelerating Discovery and Innovation through Simulation-Based Engineering and Science

    SciTech Connect

    Crabtree, George; Glotzer, Sharon; McCurdy, Bill; Roberto, Jim

    2010-07-26

    This report is based on a SC Workshop on Computational Materials Science and Chemistry for Innovation on July 26-27, 2010, to assess the potential of state-of-the-art computer simulations to accelerate understanding and discovery in materials science and chemistry, with a focus on potential impacts in energy technologies and innovation. The urgent demand for new energy technologies has greatly exceeded the capabilities of today's materials and chemical processes. To convert sunlight to fuel, efficiently store energy, or enable a new generation of energy production and utilization technologies requires the development of new materials and processes of unprecedented functionality and performance. New materials and processes are critical pacing elements for progress in advanced energy systems and virtually all industrial technologies. Over the past two decades, the United States has developed and deployed the world's most powerful collection of tools for the synthesis, processing, characterization, and simulation and modeling of materials and chemical systems at the nanoscale, dimensions of a few atoms to a few hundred atoms across. These tools, which include world-leading x-ray and neutron sources, nanoscale science facilities, and high-performance computers, provide an unprecedented view of the atomic-scale structure and dynamics of materials and the molecular-scale basis of chemical processes. For the first time in history, we are able to synthesize, characterize, and model materials and chemical behavior at the length scale where this behavior is controlled. This ability is transformational for the discovery process and, as a result, confers a significant competitive advantage. Perhaps the most spectacular increase in capability has been demonstrated in high performance computing. Over the past decade, computational power has increased by a factor of a million due to advances in hardware and software. This rate of improvement, which shows no sign of abating, has

  3. Life-Cycle Thinking in Inquiry-Based Sustainability Education--Effects on Students' Attitudes towards Chemistry and Environmental Literacy

    ERIC Educational Resources Information Center

    Juntunen, Marianne; Aksela, Maija

    2013-01-01

    The aim of the present study is to improve the quality of students' environmental literacy and sustainability education in chemistry teaching by combining the socio-scientific issue of life-cycle thinking with inquiry-based learning approaches. This case study presents results from an inquiry-based life-cycle thinking project: an interdisciplinary…

  4. Implementation of a Research-Based Lab Module in a High School Chemistry Curriculum: A Study of Classroom Dynamics

    ERIC Educational Resources Information Center

    Pilarz, Matthew

    2013-01-01

    For this study, a research-based lab module was implemented in two high school chemistry classes for the purpose of examining classroom dynamics throughout the process of students completing the module. A research-based lab module developed for use in undergraduate laboratories by the Center for Authentic Science Practice in Education (CASPiE) was…

  5. Investigating the cellular fate of a DNA-targeted platinum-based anticancer agent by orthogonal double-click chemistry.

    PubMed

    Qiao, Xin; Ding, Song; Liu, Fang; Kucera, Gregory L; Bierbach, Ulrich

    2014-03-01

    Confocal fluorescence microscopy was used to study a platinum-based anticancer agent in intact NCI-H460 lung cancer cells. Orthogonal copper-catalyzed azide-alkyne cycloaddition (click) reactions were used to simultaneously determine the cell-cycle-specific localization of the azide-functionalized platinum-acridine agent 1 and monitor its effects on nucleic acid metabolism. Copper-catalyzed postlabeling showed advantages over copper-free click chemistry using a dibenzocyclooctyne (DIBO)-modified reporter dye, which produced high background levels in microscopic images and failed to efficiently label platinum adducts in chromatin. Compound 1 was successfully labeled with the fluorophore DIBO to yield 1* (characterized by in-line high-performance liquid chromatography/electrospray mass spectrometry). 1 and 1* show a high degree of colocalization in the confocal images, but the ability of 1* to target the (compacted) chromatin was markedly reduced, most likely owing to the steric bulk introduced by the DIBO tag. Nuclear platinum levels correlated inversely with the ability of the cells to synthesize DNA and cause cell cycle arrest, as confirmed by bivariate flow cytometry analysis. In addition, a decrease in the level of cellular transcription, shrinkage of the nucleolar regions, and redistribution of RNA into the cytosol were observed. Postlabeling in conjunction with colocalization experiments is a useful tool for studying the cell killing mechanism of this type of DNA-targeted agent.

  6. Investigating the cellular fate of a DNA-targeted platinum-based anticancer agent by orthogonal double-click chemistry

    PubMed Central

    Qiao, Xin; Ding, Song; Liu, Fang; Kucera, Gregory L.

    2014-01-01

    Confocal fluorescence microscopy was used to study a platinum-based anticancer agent in intact NCI-H460 lung cancer cells. Orthogonal copper-catalyzed azide–alkyne cycloaddition (click) reactions were used to simultaneously determine the cell-cycle-specific localization of the azide-functionalized platinum–acridine agent 1 and monitor its effects on nucleic acid metabolism. Copper-catalyzed postlabeling showed advantages over copper-free click chemistry using a dibenzocyclooctyne (DIBO)-modified reporter dye, which produced high background levels in microscopic images and failed to efficiently label platinum adducts in chromatin. Compound 1 was successfully labeled with the fluorophore DIBO to yield 1* (characterized by in-line high-performance liquid chromatography/electrospray mass spectrometry). 1 and 1* show a high degree of colocalization in the confocal images, but the ability of 1* to target the (compacted) chromatin was markedly reduced, most likely owing to the steric bulk introduced by the DIBO tag. Nuclear platinum levels correlated inversely with the ability of the cells to synthesize DNA and cause cell cycle arrest, as confirmed by bivariate flow cytometry analysis. In addition, a decrease in the level of cellular transcription, shrinkage of the nucleolar regions, and redistribution of RNA into the cytosol were observed. Postlabeling in conjunction with colocalization experiments is a useful tool for studying the cell killing mechanism of this type of DNA-targeted agent. PMID:24407462

  7. Fragment Screening of Soluble Epoxide Hydrolase for Lead Generation-Structure-Based Hit Evaluation and Chemistry Exploration.

    PubMed

    Xue, Yafeng; Olsson, Thomas; Johansson, Carina A; Öster, Linda; Beisel, Hans-Georg; Rohman, Mattias; Karis, David; Bäckström, Stefan

    2016-03-04

    Soluble epoxide hydrolase (sEH) is involved in the regulation of many biological processes by metabolizing the key bioactive lipid mediator, epoxyeicosatrienoic acids. For the development of sEH inhibitors with improved physicochemical properties, we performed both a fragment screening and a high-throughput screening aiming at an integrated hit evaluation and lead generation. Followed by a joint dose-response analysis to confirm the hits, the identified actives were then effectively triaged by a structure-based hit-classification approach to three prioritized series. Two distinct scaffolds were identified as tractable starting points for potential lead chemistry work. The oxoindoline series bind at the right-hand side of the active-site pocket with hydrogen bonds to the protein. The 2-phenylbenzimidazole-4-sulfonamide series bind at the central channel with significant induced fit, which has not been previously reported. On the basis of the encouraging initial results, we envision that a new lead series with improved properties could be generated if a vector is found that could merge the cyclohexyl functionality of the oxoindoline series with the trifluoromethyl moiety of the 2-phenylbenzimidazole-4-sulfonamide series.

  8. Coupled Phenomena in Chemistry.

    ERIC Educational Resources Information Center

    Matsubara, Akira; Nomura, Kazuo

    1979-01-01

    Various phenomena in chemistry and biology can be understood through Gibbs energy utilization. Some common phenomena in chemistry are explained including neutralization, hydrolysis, oxidation and reaction, simultaneous dissociation equilibrium of two weak acids, and common ion effect on solubility. (Author/SA)

  9. 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.

  10. Determination of acidity constants of acid-base indicators by second-derivative spectrophotometry

    NASA Astrophysics Data System (ADS)

    Kara, Derya; Alkan, Mahir

    2000-12-01

    A method for calculation of acid-base dissociation constants of monoprotic weak organic acids whose acid and base species have overlapping spectra from absorptiometric and pH measurements is described. It has been shown that the second-derivative spectrophotometry can effectively be used for determining the dissociation constants, when dissociation constants obtained for methyl orange and bromothymol blue were compared with the values given in the literature.

  11. Graphical representations of the chemistry of garnets in a three-dimensional MATLAB based provenance plot

    NASA Astrophysics Data System (ADS)

    Knierzinger, Wolfgang; Palzer, Markus; Wagreich, Michael; Meszar, Maria; Gier, Susanne

    2016-04-01

    A newly developed, MATLAB based garnet provenance plot allows a three-dimensional tetrahedral representation of the chemistry of garnets for the endmembers almandine, pyrope, spessartine and grossular. Based on a freely accessible database of Suggate & Hall (2013) and additional EPMA-data on the internet, the chemistry of more than 2500 garnets was evaluated and used to create various subfields that correspond to different facies conditions of metapelitic, metasomatic and metaigneous rocks as well as granitic rocks. These triangulated subfields act as reference structures within the tetrahedron, facilitating assignments of garnet chemistries to different lithologies. In comparison with conventional tenary garnet discrimination diagrams by Mange & Morton (2007), Wright/Preston et al. (1938/2002) and Aubrecht et al. (2009), this tetrahedral provenance plot enables a better assessment of the conditions of formation of garnets by reducing the overlapping of certain subfields. In particular, a clearer distinction between greenschist facies rocks, amphibolite facies rocks and granitic rocks can be achieved. First applications of the tetrahedral garnet plot provided new insights on sedimentary processes during the Lower Miocene in the pre-Alpine Molasse basin. Bibliography Aubrecht, R., Meres, S., Sykora, M., Mikus, T. (2009). Provenance of the detrital garnets and spinels from the Albian sediments of the Czorsztyn Unit (Pieniny Klippen Belt , Western Carpathians, Slovakia). In: Geologica Carpathica, Dec. 2009, 60, 6, pp. 463-483. Mange, M.A., Morton, A.C. (2007). Geochemistry of Heavy Minerals. In: Mange, M.A. & Wright, D.T.(2007).Heavy Minerals in Use, Amsterdam, pp. 345-391. Preston, J., Hartley, A., Mange-Rajetzky, M., Hole, M., May, G., Buck, S., Vaughan, L. (2002). The provenance of Triassic continental sandstones from the Beryl Field, northern North Sea: Mineralogical, geochemical and sedimentological constraints. In: Journal of Sedimentary Research, 72, pp. 18

  12. Comprehensive Review in Current Developments of Benzimidazole-Based Medicinal Chemistry.

    PubMed

    Keri, Rangappa S; Hiremathad, Asha; Budagumpi, Srinivasa; Nagaraja, Bhari Mallanna

    2015-07-01

    The properties of benzimidazole and its derivatives have been studied over more than one hundred years. Benzimidazole derivatives are useful intermediates/subunits for the development of molecules of pharmaceutical or biological interest. Substituted benzimidazole derivatives have found applications in diverse therapeutic areas such as antiulcer, anticancer agents, and anthelmintic species to name just a few. This work systematically gives a comprehensive review in current developments of benzimidazole-based compounds in the whole range of medicinal chemistry as anticancer, antibacterial, antifungal, anti-inflammatory, analgesic agents, anti-HIV, antioxidant, anticonvulsant, antitubercular, antidiabetic, antileishmanial, antihistaminic, antimalarial agents, and other medicinal agents. This review will further be helpful for the researcher on the basis of substitution pattern around the nucleus with an aim to help medicinal chemists for developing an SAR on benzimidazole drugs/compounds.

  13. Silver/polysaccharide-based nanofibrous materials synthesized from green chemistry approach.

    PubMed

    Martínez-Rodríguez, M A; Garza-Navarro, M A; Moreno-Cortez, I E; Lucio-Porto, R; González-González, V A

    2016-01-20

    In this contribution a novel green chemistry approach for the synthesis of nanofibrous materials based on blends of carboxymethyl-cellulose (CMC)-silver nanoparticles (AgNPs) composite and polyvinyl-alcohol (PVA) is proposed. These nanofibrous materials were obtained from the electrospinning of blends of aqueous solutions of CMC-AgNPs composite and PVA, which were prepared at different CMC/PVA weight ratios in order to electrospin nanofibers applying a constant tension of 15kV. The synthesized materials were characterized by means of transmission electron microscopy, scanning electron microscopy; as well as Fourier-transform infrared, ultraviolet and Raman spectroscopic techniques. Experimental evidence suggests that the diameter of the nanofibers is thinner than any other reported in the literature regarding the electrospinning of CMC. This feature is related to the interactions of AgNPs with carboxyl functional groups of the CMC, which diminish those between the later and acetyl groups of PVA.

  14. Organic chemistry and immunochemical strategies in the design of potent carbohydrate-based vaccines.

    PubMed

    Roy, René; Shiao, Tze Chieh

    2011-01-01

    A brief overview of carbohydrate antigens processing and uptakes involved in the adaptive immune system is highlighted. To counter balance the poor immunogenicity and T-cell independent characteristics of carbohydrate antigens, chemists have developed original hybrid molecules aimed at targeting specific competent immune cell receptors. Amongst several potential vaccine candidates dedicated against diseases, this short report will focused on those most advance and state of the art organic chemistry involved therein. One case has led to the first example of a commercial vaccine entirely prepared from a synthetic carbohydrate antigen against infections caused by the Gram-negative bacteria Haemophilus influenza type b responsible for pneumonia and acute bacterial meningitis in infants. Other commendable examples will illustrate the immunochemical strategies engaged in the development of anticancer carbohydrate-based vaccines.

  15. Effects of simulated acid rain on soil and soil solution chemistry in a monsoon evergreen broad-leaved forest in southern China.

    PubMed

    Qiu, Qingyan; Wu, Jianping; Liang, Guohua; Liu, Juxiu; Chu, Guowei; Zhou, Guoyi; Zhang, Deqiang

    2015-05-01

    Acid rain is an environmental problem of increasing concern in China. In this study, a laboratory leaching column experiment with acid forest soil was set up to investigate the responses of soil and soil solution chemistry to simulated acid rain (SAR). Five pH levels of SAR were set: 2.5, 3.0, 3.5, 4.0, and 4.5 (as a control, CK). The results showed that soil acidification would occur when the pH of SAR was ≤3.5. The concentrations of NO₃(-)and Ca(2+) in the soil increased significantly when the pH of SAR fell 3.5. The concentration of SO₄(2-) in the soil increased significantly when the pH of SAR was <4.0. The effects of SAR on soil solution chemistry became increasingly apparent as the experiment proceeded (except for Na(+) and dissolved organic carbon (DOC)). The net exports of NO₃(-), SO₄(2-), Mg(2+), and Ca(2+) increased about 42-86% under pH 2.5 treatment as compared to CK. The Ca(2+) was sensitive to SAR, and the soil could release Ca(2+) through mineral weathering to mitigate soil acidification. The concentration of exchangeable Al(3+) in the soil increased with increasing the acidity of SAR. The releases of soluble Al and Fe were SAR pH dependent, and their net exports under pH 2.5 treatment were 19.6 and 5.5 times, respectively, higher than that under CK. The net export of DOC was reduced by 12-29% under SAR treatments as compared to CK. Our results indicate the chemical constituents in the soil are more sensitive to SAR than those in the soil solution, and the effects of SAR on soil solution chemistry depend not only on the intensity of SAR but also on the duration of SAR addition. The soil and soil solution chemistry in this region may not be affected by current precipitation (pH≈4.5) in short term, but the soil and soil leachate chemistry may change dramatically if the pH of precipitation were below 3.5 and 3.0, respectively.

  16. Chip-based sequencing nucleic acids

    DOEpatents

    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.

  17. The Effect of Level of Information as Presented by Different Technologies on Students' Understanding of Acid, Base, and pH Concepts.

    ERIC Educational Resources Information Center

    Nakhleh, Mary B.; Krajcik, Joseph S.

    Within high school chemistry the topic of acids, bases, and pH is particularly challenging because robust understanding of the topic depends heavily on the student possessing deep concepts of atoms, molecules, ions, and chemical reactions. Since knowledge is acquired and stored in a dynamic structure, it was investigated in this study how…

  18. An Experimental Evaluation of Programed Instruction as One of Two Review Techniques for Two-Year College Students Concerned with Solving Acid-Base Chemical Equilibrium Problems.

    ERIC Educational Resources Information Center

    Sharon, Jared Bear

    The major purpose of this study was to design and evaluate a programed instructional unit for a first year college chemistry course. The topic of the unit was the categorization and solution of acid-base equilibria problems. The experimental programed instruction text was used by 41 students and the fifth edition of Schaum's Theory and Problems of…

  19. Sol-gel chemistry-based Ucon-coated columns for capillary electrophoresis.

    PubMed

    Hayes, J D; Malik, A

    1997-07-18

    A sol-gel chemistry-based novel approach for the preparation of a Ucon-coated fused-silica capillary column in capillary electrophoresis is presented. In this approach the sol-gel process is carried out inside 25 microm I.D. fused-silica capillaries. The sol solution contained appropriate quantities of an alkoxide-based sol-gel precursor, a polymeric coating material (Ucon), a crosslinking reagent, a surface derivatizing reagent, controlled amounts of water and a catalyst dissolved in a suitable solvent system. The coating procedure involves filling a capillary with the sol solution and allowing the sol-gel process to proceed for an optimum period. Hydrolysis of the alkoxide precursor and polycondensation of the hydrolyzed products with the surface silanol groups and the hydroxy-terminated Ucon molecules lead to the formation of a surface-bonded sol-gel coating on the inner walls of the capillary. The thickness of the coated film can be controlled by varying the reaction time, coating solution composition and experimental conditions. Commercial availability of high purity sol-gel precursors (e.g., TEOS 99.999%), the ease of coating, run-to-run and column-to-column reproducibility, and long column lifetimes make sol-gel coating chemistry very much suitable for being applied in analytical microseparations column technology. Test samples of basic proteins and nucleotides were used to evaluate the column performance. These results show that the sol-gel coating scheme has allowed for the generation of bio-compatible surfaces characterized by high separation efficiencies in CE. For different types of solutes, the sol-gel coated Ucon column consistently provided migration time R.S.D. values of the order of 0.5%.

  20. 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.