Nano-sized metabolic precursors for heterogeneous tumor-targeting strategy using bioorthogonal click chemistry in vivo.

Science.gov (United States)

Lee, Sangmin; Jung, Seulhee; Koo, Heebeom; Na, Jin Hee; Yoon, Hong Yeol; Shim, Man Kyu; Park, Jooho; Kim, Jong-Ho; Lee, Seulki; Pomper, Martin G; Kwon, Ick Chan; Ahn, Cheol-Hee; Kim, Kwangmeyung

2017-12-01

Herein, we developed nano-sized metabolic precursors (Nano-MPs) for new tumor-targeting strategy to overcome the intrinsic limitations of biological ligands such as the limited number of biological receptors and the heterogeneity in tumor tissues. We conjugated the azide group-containing metabolic precursors, triacetylated N-azidoacetyl-d-mannosamine to generation 4 poly(amidoamine) dendrimer backbone. The nano-sized dendrimer of Nano-MPs could generate azide groups on the surface of tumor cells homogeneously regardless of cell types via metabolic glycoengineering. Importantly, these exogenously generated 'artificial chemical receptors' containing azide groups could be used for bioorthogonal click chemistry, regardless of phenotypes of different tumor cells. Furthermore, in tumor-bearing mice models, Nano-MPs could be mainly localized at the target tumor tissues by the enhanced permeation and retention (EPR) effect, and they successfully generated azide groups on tumor cells in vivo after an intravenous injection. Finally, we showed that these azide groups on tumor tissues could be used as 'artificial chemical receptors' that were conjugated to bioorthogonal chemical group-containing liposomes via in vivo click chemistry in heterogeneous tumor-bearing mice. Therefore, overall results demonstrated that our nano-sized metabolic precursors could be extensively applied to new alternative tumor-targeting technique for molecular imaging and drug delivery system, regardless of the phenotype of heterogeneous tumor cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

Science.gov (United States)

Chung Kwong, Kai; Chim, Man Mei; Davies, James F.; Wilson, Kevin R.; Nin Chan, Man

2018-02-01

Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this work investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH3SO4Na) droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH) of 85 %. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time, DART) coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO4-) has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH2O) and a sulfate radical anion (SO4 ṡ -) upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19) × 10-13 cm3 molecule-1 s-1 with an effective OH uptake coefficient, γeff, of 0.17 ± 0.03. While about 40 % of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27 × 1012 molecule cm-3 s), only a 3 % decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we firstly demonstrate that the heterogeneous OH oxidation of an

Selective Oxidations using Nanostructured Heterogeneous Catalysts

DEFF Research Database (Denmark)

Mielby, Jerrik Jørgen

and because they produce H2O as the only by-product. Chapter 1 gives a short introduction to basic concepts in heterogeneous catalysis and green chemistry. Furthermore, the chapter gives an overview of the most important strategies to synthesise functional nanostructured materials and highlights how detailed......The aim of this thesis is to investigate and develop new efficient methods to oxidise alcohols and amines using heterogeneous catalysts and either O2 or H2O2 as oxidants. From an economic and environmental point of view, these oxidants are ideal, because they are cheap and readily available...... understanding of size, shape and structure can help in the development of new and more efficient heterogeneous catalysts. The chapter is not intended to give a complete survey, but rather to introduce some of the recent developments in the synthesis of nanostructured heterogeneous catalysts. Finally...

Hydrogen chloride heterogeneous chemistry on frozen water particles in subsonic aircraft plume. Laboratory studies and modelling

Energy Technology Data Exchange (ETDEWEB)

Persiantseva, N.V.; Popovitcheva, O.B.; Rakhimova, T.V. [Moscow State Univ. (Russian Federation)

1997-12-31

Heterogeneous chemistry of HCl, as a main reservoir of chlorine content gases, has been considered after plume cooling and ice particle formation. The HCl, HNO{sub 3}, N{sub 2}O{sub 5} uptake efficiencies by frozen water were obtained in a Knudsen-cell flow reactor at the subsonic cruise conditions. The formation of ice particles in the plume of subsonic aircraft is simulated to describe the kinetics of gaseous HCl loss due to heterogeneous processes. It is shown that the HCl uptake by frozen water particles may play an important role in the gaseous HCl depletion in the aircraft plume. (author) 14 refs.

Hydrogen chloride heterogeneous chemistry on frozen water particles in subsonic aircraft plume. Laboratory studies and modelling

Energy Technology Data Exchange (ETDEWEB)

Persiantseva, N V; Popovitcheva, O B; Rakhimova, T V [Moscow State Univ. (Russian Federation)

1998-12-31

Heterogeneous chemistry of HCl, as a main reservoir of chlorine content gases, has been considered after plume cooling and ice particle formation. The HCl, HNO{sub 3}, N{sub 2}O{sub 5} uptake efficiencies by frozen water were obtained in a Knudsen-cell flow reactor at the subsonic cruise conditions. The formation of ice particles in the plume of subsonic aircraft is simulated to describe the kinetics of gaseous HCl loss due to heterogeneous processes. It is shown that the HCl uptake by frozen water particles may play an important role in the gaseous HCl depletion in the aircraft plume. (author) 14 refs.

Density functional theory in surface chemistry and catalysis

DEFF Research Database (Denmark)

Nørskov, Jens Kehlet; Abild-Pedersen, Frank; Studt, Felix

2011-01-01

Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future...

Research needs and opportunities in radiation chemistry workshop

Energy Technology Data Exchange (ETDEWEB)

Barbara, Paul F

1998-04-19

There is a growing urgency for forefront basic research on ionizing radiation-induced chemical reactions, due to the relevance of these reactions in such areas of critical national need as environmental waste management, environmental remediation, nuclear energy production, and medical diagnosis and radiation therapy. Fortunately, the emergence of new theoretical and experimental tools for the study of radiation-induced chemical and physical processes, i.e. Radiation Chemistry, makes future progress quite promising. Nevertheless, a recent decline in he number of young investigators in radiation chemistry, as well as a natural obsolescence of large research facilities in radiation chemistry are serious obstacles to further progress. Understanding radiation-induced processes is of vital significance in such diverse fields as waste remediation in environmental cleanup, radiation processing of polymers and food, medical diagnosis and therapy, catalysis of chemical reactions, environmentally benign synthesis, and nuclear energy production. Radiation chemistry provides for these fields fundamental quantitative data, such as reaction rate coefficients, diffusion coefficients, radiation chemical yields, etc. As well as providing useful quantitative information of technological and medical importance, radiation chemistry is also a valuable tool for solving fundamental problems in chemistry and in material sciences. Exploiting the many facets of radiation chemistry requires a thorough and comprehensive understanding of the underlying chemical and physical processes. An understanding of the structure and dynamics of “tracks” produced by ionizing radiation is a central issue in the field. There is a continuing need to study the ultrafast processes that link the chemistry and physics of radiation-induced phenomena. This is especially true for practically important, but less well understood, nonstandard environments such as interfacial systems, supercritical media, and

Student understanding development in chemistry concepts through constructivist-informed laboratory and science camp process in secondary school

Science.gov (United States)

Pathommapas, Nookorn

2018-01-01

Science Camp for Chemistry Concepts was the project which designed to provide local students with opportunities to apply chemistry concepts and thereby developing their 21st century skills. The three study purposes were 1) to construct and develop chemistry stations for encouraging students' understandings in chemistry concepts based on constructivist-informed laboratory, 2) to compare students' understandings in chemistry concepts before and after using chemistry learning stations, and 3) to study students' satisfactions of using their 21st century skills in science camp activities. The research samples were 67 students who attended the 1-day science camp. They were levels 10 to 11 students in SumsaoPittayakarn School, UdonThani Province, Thailand. Four constructivist-informed laboratory stations of chemistry concepts were designed for each group. Each station consisted of a chemistry scenario, a question, answers in tier 1 and supporting reasons in tier 2, and 4 sets of experimental instruments. Four to five-member subgroups of four student groups parallel participated in laboratory station for an hour in each station. Student activities in each station concluded of individual pretest, group prediction, experimental design, testing out and collection data, interpreting the results, group conclusion, and individual post-test. Data collection was done by station mentors using two-tier multiple choice questions, students' written work and interviews. Data triangulation was used for interpreting and confirming students' understandings of chemistry concepts which divided into five levels, Sound Understanding (SU), Partial Understanding (PU), Specific Misconception (SM), No Understanding (NU) and No Response (NR), before and after collaborating at each station. The study results found the following: 1) four constructivist-laboratory stations were successfully designed and used to investigate student' understandings in chemistry concepts via collaborative workshop of

Session 4: The influence of elementary heterogeneous reforming chemistry within solid-oxide fuel cell anodes

Energy Technology Data Exchange (ETDEWEB)

Zhu, H.; Kee, R.J. [Engineering Division, Colorado School of Mines, Golden, CO (United States); Janardhanan, V.M.; Deutschmann, O. [Karlsruhe Univ., Institute for Chemical Technology (Germany); Goodwin, D.G. [Engineering and Applied Science., California Inst. of Technology, Pasadena, CA (United States); Sullivan, N.P. [ITN Energy Systems, Littleton, CO (United States)

2004-07-01

In the work presented a computational model is developed that represents the coupled effects of fluid flow in fuel channels, porous media transport and chemistry in the anode, and electrochemistry associated with the membrane-electrode assembly. An important objective is to explore the role of heterogeneous chemistry within the anode. In addition to cell electrical performance the chemistry model predicts important behaviors like catalyst-fouling deposit formation (i.e., coking). The model is applied to investigate alternative fuel-cell operating conditions, including varying fuel flow rates, adding air to the fuel stream, and recirculating exhaust gases. Results include assessments of performance metrics like fuel utilization, cell efficiency, power density, and catalyst coking. The model shows that 'direct electrochemical oxidation' of hydrocarbon fuels in solid-oxide fuel cells can be explained by a process that involves reforming the fuel to H{sub 2}, with hydrogen being the only species responsible for charge exchange. The model can be applied to investigate alternative design and operating conditions, seeking to improve the overall performance. (O.M.)

University Students' Understanding of Chemistry Processes and the Quality of Evidence in Their Written Arguments

Science.gov (United States)

Seung, Eulsun; Choi, Aeran; Pestel, Beverly

2016-01-01

We have developed a process-oriented chemistry laboratory curriculum for non-science majors. The purpose of this study is both to explore university students' understanding of chemistry processes and to evaluate the quality of evidence students use to support their claims regarding chemistry processes in a process-oriented chemistry laboratory…

The Contribution of Constructivist Instruction Accompanied by Concept Mapping in Enhancing Pre-Service Chemistry Teachers' Conceptual Understanding of Chemistry in the Laboratory Course

Science.gov (United States)

Aydin, Sevgi; Aydemir, Nurdane; Boz, Yezdan; Cetin-Dindar, Ayla; Bektas, Oktay

2009-01-01

The present study aimed to evaluate whether a chemistry laboratory course called "Laboratory Experiments in Science Education" based on constructivist instruction accompanied with concept mapping enhanced pre-service chemistry teachers' conceptual understanding. Data were collected from five pre-service chemistry teachers at a university…

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

Directory of Open Access Journals (Sweden)

K. C. Kwong

2018-02-01

Full Text Available Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this work investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH3SO4Na droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH of 85 %. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time, DART coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO4− has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH2O and a sulfate radical anion (SO4 ⋅ − upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19  ×  10−13 cm3 molecule−1 s−1 with an effective OH uptake coefficient, γeff, of 0.17 ± 0.03. While about 40 % of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27  ×  1012 molecule cm−3 s, only a 3 % decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume V – heterogeneous reactions on solid substrates

Directory of Open Access Journals (Sweden)

J. N. Crowley

2010-09-01

Full Text Available This article, the fifth in the ACP journal series, presents data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the heterogeneous processes on surfaces of solid particles present in the atmosphere, for which uptake coefficients and adsorption parameters have been presented on the IUPAC website in 2010. The article consists of an introduction and guide to the evaluation, giving a unifying framework for parameterisation of atmospheric heterogeneous processes. We provide summary sheets containing the recommended uptake parameters for the evaluated processes. Four substantial appendices contain detailed data sheets for each process considered for ice, mineral dust, sulfuric acid hydrate and nitric acid hydrate surfaces, which provide information upon which the recommendations are made.

WRF-Chem model predictions of the regional impacts of N2O5 heterogeneous processes on night-time chemistry over north-western Europe

Directory of Open Access Journals (Sweden)

D. Lowe

2015-02-01

Full Text Available Chemical modelling studies have been conducted over north-western Europe in summer conditions, showing that night-time dinitrogen pentoxide (N2O5 heterogeneous reactive uptake is important regionally in modulating particulate nitrate and has a~modest influence on oxidative chemistry. Results from Weather Research and Forecasting model with Chemistry (WRF-Chem model simulations, run with a detailed volatile organic compound (VOC gas-phase chemistry scheme and the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC sectional aerosol scheme, were compared with a series of airborne gas and particulate measurements made over the UK in July 2010. Modelled mixing ratios of key gas-phase species were reasonably accurate (correlations with measurements of 0.7–0.9 for NO2 and O3. However modelled loadings of particulate species were less accurate (correlation with measurements for particulate sulfate and ammonium were between 0.0 and 0.6. Sulfate mass loadings were particularly low (modelled means of 0.5–0.7 μg kg−1air, compared with measurements of 1.0–1.5 μg kg−1air. Two flights from the campaign were used as test cases – one with low relative humidity (RH (60–70%, the other with high RH (80–90%. N2O5 heterogeneous chemistry was found to not be important in the low-RH test case; but in the high-RH test case it had a strong effect and significantly improved the agreement between modelled and measured NO3 and N2O5. When the model failed to capture atmospheric RH correctly, the modelled NO3 and N2O5 mixing ratios for these flights differed significantly from the measurements. This demonstrates that, for regional modelling which involves heterogeneous processes, it is essential to capture the ambient temperature and water vapour profiles. The night-time NO3 oxidation of VOCs across the whole region was found to be 100–300 times slower than the daytime OH oxidation of these compounds. The difference in contribution was less

Heterogenous phase as a mean in combinatorial chemistry

International Nuclear Information System (INIS)

Abdel-Hamid, S.G.

2007-01-01

Combinatorial chemistry is a rapid and inexpensive technique for the synthesis of hundreds of thousands of organic compounds of potential medicinal activity. In the past few decades a large number of combinatorial libraries have been constructed, and significantly supplement the chemical diversity of the traditional collections of the potentially active medicinal compounds. Solid phase synthesis was used to enrich the combinatorial chemistry libraries, through the use of solid supports (resins) and their modified forms. Most of the new libraries of compounds appeared recently, were synthesized by the use of solid-phase. Solid-phase combinatorial chemistry (SPCC) is now considered as an outstanding branch in pharmaceutical chemistry research and used extensively as a tool for drug discovery within the context of high-throughput chemical synthesis. The best pure libraries synthesized by the use of solid phase combinatorial chemistry (SPCC) may well be those of intermediate complexity that are free of artifact-causing nuisance compounds. (author)

Heterogeneous Catalysis: Understanding for Designing, and Designing for Applications

OpenAIRE

Corma Canós, Avelino

2016-01-01

Despite the introduction of high-throughput and combinatorial methods that certainly can be useful in the process of catalysts optimization, it is recognized that the generation of fundamental knowledge at the molecular level is key for the development of new concepts and for reaching the final objective of solid catalysts by design … Corma Canós, A. (2016). Heterogeneous Catalysis: Understanding for Designing, and Designing for Applications. Angewandte Chemie International Edition. 55(21)...

Culture of peace and care for the Planet Earth as predictors of students’ understanding of chemistry concepts

Directory of Open Access Journals (Sweden)

Ngozi Okafor

2016-05-01

Full Text Available This study focused on how culture of peace and care for the planet earth variables predicted public coeducational secondary school students understanding of chemistry concepts in Anambra State of Nigeria. Three research questions guided the study. It was a survey and correlational research designs that involved sample of 180 drawn from six schools through a three-stage sampling procedures. Culture of Peace and Care for the Planet Earth Questionnaire (CPCPEQ and Chemistry Understanding Test (CUT were used for data collection. Their validity and reliability were determined using Cronbach alpha and Kuder-Richardson formula 20 which gave indices of r=.71 and r= 0.78 respectively. Linear regression and bivariate correlation analyses as well as One-way analysis of variance (ANOVA were used in data analysis. The results showed that for culture of peace, tolerance significantly predicted higher chemistry concepts scores while social movement significantly predicted lower concepts scores on chemistry understanding test. On care for the planet earth, adjusting thermostat significantly predicted higher scores while saving water significantly predicted lower scores on chemistry understanding test. The study recommended setting- up of Visionary Chemists for Environment and Peace Culture (VCEPC in all schools that would sensitize students on how to shun hostility, indoctrination and embracing effective methods of waste disposal. It concludes that everybody should go green, plant more trees, and promote mutual understanding, tolerance, peaceful co-existence and friendly environments as fundamental tips of peace culture and care for the planet earth that foster meaningful understanding of chemistry concepts among secondary school students.

Using digital technologies to enhance chemistry students' understanding and representational skills

DEFF Research Database (Denmark)

Hilton, Annette

Abstract Chemistry students need to understand chemistry on molecular, symbolic and macroscopic levels. Students find it difficult to use representations on these three levels to interpret and explain data. One approach is to encourage students to use writing-to-learn strategies in inquiry settings...... to present and interpret their laboratory results. This paper describes findings from a study on the effects on students’ learning outcomes of creating multimodal texts to report on laboratory inquiries. The study involved two senior secondary school chemistry classes (n = 22, n = 27). Both classes completed...... representations to make explanations on the molecular level. Student interviews and classroom video-recordings suggested that using digital resources to create multimodal texts promoted knowledge transformation and hence deeper reflection on the meaning of data and representations. The study has implications...

Analysis of the effect of specific vocabulary instruction on high school chemistry students' knowledge and understanding

Science.gov (United States)

Labrosse, Peggy

The purpose of this study was to analyze the effects of specific vocabulary instruction on high school chemistry students' knowledge and understanding. Students might be able to formally recite a definition for a term without actually having understood the meaning of the term and its connection to other terms or to related concepts. Researchers (Cassels & Johnstone, 1983; Gabel, 1999; Johnstone, 1991) have been studying the difficulty students have in learning science, particularly chemistry. Gabel (1999) suggests that, "while research into misconceptions (also known as alternative conceptions) and problem-solving has dominated the field for the past 25 years, we are no closer to a solution that would improve the teaching and learning of chemistry" (P. 549). Gabel (1999) relates the difficulty in learning chemistry to use of language. She refers to student difficulty both with words that have more than one meaning in English and with words that are used to mean one idea in chemistry and another idea in every day language. The Frayer Model, a research-based teaching strategy, is a graphic organizer which students use to create meaningful definitions for terms in context (Frayer, Frederick, & Klausmeier, 1969). It was used as the treatment---the specific vocabulary instruction---in this research study. The researcher collected and analyzed data to answer three research questions that focused on the effect of using the Frayer model (a graphic organizer) on high school students' knowledge and understanding of academic language used in chemistry. The research took place in a New England high school. Four intact chemistry classes provided the student participants; two classes were assigned to the treatment group (TG) and two classes were assigned to the control group (CG). The TG received vocabulary instruction on 14 chosen terms using the Frayer Model. The CG received traditional vocabulary instruction with no special attention to the 14 terms selected for this study

Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

International Nuclear Information System (INIS)

Casey, C.P.

1994-07-01

Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving η 5 -to η 1 -cyclopentadienyl ring slippage in catalysis was completed

Recent Advances in Atmospheric Chemistry of Mercury

Directory of Open Access Journals (Sweden)

Lin Si

2018-02-01

Full Text Available Mercury is one of the most toxic metals and has global importance due to the biomagnification and bioaccumulation of organomercury via the aquatic food web. The physical and chemical transformations of various mercury species in the atmosphere strongly influence their composition, phase, transport characteristics and deposition rate back to the ground. Modeling efforts to assess global cycling of mercury require an accurate understanding of atmospheric mercury chemistry. Yet, there are several key uncertainties precluding accurate modeling of physical and chemical transformations. We focus this article on recent studies (since 2015 on improving our understanding of the atmospheric chemistry of mercury. We discuss recent advances in determining the dominant atmospheric oxidant of elemental mercury (Hg0 and understanding the oxidation reactions of Hg0 by halogen atoms and by nitrate radical (NO3—in the aqueous reduction of oxidized mercury compounds (HgII as well as in the heterogeneous reactions of Hg on atmospheric-relevant surfaces. The need for future research to improve understanding of the fate and transformation of mercury in the atmosphere is also discussed.

Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

Energy Technology Data Exchange (ETDEWEB)

Casey, C.P.

1994-07-01

Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving {eta}{sup 5}-to {eta}{sup 1}-cyclopentadienyl ring slippage in catalysis was completed.

Recent progress in understanding activity cliffs and their utility in medicinal chemistry.

Science.gov (United States)

Stumpfe, Dagmar; Hu, Ye; Dimova, Dilyana; Bajorath, Jürgen

2014-01-09

The activity cliff concept is of high relevance for medicinal chemistry. Recent studies are discussed that have further refined our understanding of activity cliffs and suggested different ways of exploiting activity cliff information. These include alternative approaches to define and classify activity cliffs in two and three dimensions, data mining investigations to systematically detect all possible activity cliffs, the introduction of computational methods to predict activity cliffs, and studies designed to explore activity cliff progression in medicinal chemistry. The discussion of these studies is complemented with new findings revealing the frequency of activity cliff formation when different molecular representations are used and the distribution of activity cliffs across different targets. Taken together, the results have a number of implications for the practice of medicinal chemistry.

Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

Energy Technology Data Exchange (ETDEWEB)

Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

2015-09-14

Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co₃O₄ or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

The use of molecular imaging combined with genomic techniques to understand the heterogeneity in cancer metastasis

Science.gov (United States)

Chowdhury, R; Ganeshan, B; Irshad, S; Lawler, K; Eisenblätter, M; Milewicz, H; Rodriguez-Justo, M; Miles, K; Ellis, P; Groves, A; Punwani, S

2014-01-01

Tumour heterogeneity has, in recent times, come to play a vital role in how we understand and treat cancers; however, the clinical translation of this has lagged behind advances in research. Although significant advancements in oncological management have been made, personalized care remains an elusive goal. Inter- and intratumour heterogeneity, particularly in the clinical setting, has been difficult to quantify and therefore to treat. The histological quantification of heterogeneity of tumours can be a logistical and clinical challenge. The ability to examine not just the whole tumour but also all the molecular variations of metastatic disease in a patient is obviously difficult with current histological techniques. Advances in imaging techniques and novel applications, alongside our understanding of tumour heterogeneity, have opened up a plethora of non-invasive biomarker potential to examine tumours, their heterogeneity and the clinical translation. This review will focus on how various imaging methods that allow for quantification of metastatic tumour heterogeneity, along with the potential of developing imaging, integrated with other in vitro diagnostic approaches such as genomics and exosome analyses, have the potential role as a non-invasive biomarker for guiding the treatment algorithm. PMID:24597512

MURI: An Integrated Multi-Scale Approach for Understanding Ion Transport in Complex Heterogeneous Organic Materials

Science.gov (United States)

2017-09-30

Thomas A. Witten,f Matthew W. Liberatore,a and Andrew M. Herring,a,* a Department of Chemical and Biological Engineering and bDepartment of Chemistry ...2) To fundamentally understand, with combined experimental and computational approaches, the interplay of chemistry , processing, and morphology on...Society, The International Society of Electrochemistry and The American Institute of Chemical Engineers to give oral and poster presentations. In

Catalysis by Design: Well-Defined Single-Site Heterogeneous Catalysts

KAUST Repository

Pelletier, Jeremie

2016-03-09

ConspectusHeterogeneous catalysis, a field important industrially and scientifically, is increasingly seeking and refining strategies to render itself more predictable. The main issue is due to the nature and the population of catalytically active sites. Their number is generally low to very low, their "acid strengths" or " redox properties" are not homogeneous, and the material may display related yet inactive sites on the same material. In many heterogeneous catalysts, the discovery of a structure-activity reationship is at best challenging. One possible solution is to generate single-site catalysts in which most, if not all, of the sites are structurally identical. Within this context and using the right tools, the catalyst structure can be designed and well-defined, to reach a molecular understanding. It is then feasible to understand the structure-activity relationship and to develop predictable heterogeneous catalysis. Single-site well-defined heterogeneous catalysts can be prepared using concepts and tools of surface organometallic chemistry (SOMC). This approach operates by reacting organometallic compounds with surfaces of highly divided oxides (or of metal nanoparticles). This strategy has a solid track record to reveal structure-activity relationship to the extent that it is becoming now quite predictable. Almost all elements of the periodical table have been grafted on surfaces of oxides (from simple oxides such as silica or alumina to more sophisticated materials regarding composition or porosity).Considering catalytic hydrocarbon transformations, heterogeneous catalysis outcome may now be predicted based on existing mechanistic proposals and the rules of molecular chemistry (organometallic, organic) associated with some concepts of surface sciences. A thorough characterization of the grafted metal centers must be carried out using tools spanning from molecular organometallic or surface chemistry. By selection of the metal, its ligand set, and the

Molecular ingredients of heterogeneous catalysis

International Nuclear Information System (INIS)

Somorjai, G.A.

1982-06-01

The purpose of this paper is to present a review and status report to those in theoretical chemistry of the rapidly developing surface science of heterogeneous catalysis. The art of catalysis is developing into science. This profound change provides one with opportunities not only to understand the molecular ingredients of important catalytic systems but also to develop new and improved catalyst. The participation of theorists to find answers to important questions is sorely needed for the sound development of the field. It is the authors hope that some of the outstanding problems of heterogeneous catalysis that are identified in this paper will be investigated. For this purpose the paper is divided into several sections. The brief Introduction to the methodology and recent results of the surface science of heterogeneous catalysis is followed by a review of the concepts of heterogeneous catalysis. Then, the experimental results that identified the three molecular ingredients of catalysis, structure, carbonaceous deposit and the oxidation state of surface atoms are described. Each section is closed with a summary and a list of problems that require theoretical and experimental scrutiny. Finally attempts to build new catalyst systems and the theoretical and experimental problems that appeared in the course of this research are described

Molecular ingredients of heterogeneous catalysis

Energy Technology Data Exchange (ETDEWEB)

Somorjai, G.A.

1982-06-01

The purpose of this paper is to present a review and status report to those in theoretical chemistry of the rapidly developing surface science of heterogeneous catalysis. The art of catalysis is developing into science. This profound change provides one with opportunities not only to understand the molecular ingredients of important catalytic systems but also to develop new and improved catalyst. The participation of theorists to find answers to important questions is sorely needed for the sound development of the field. It is the authors hope that some of the outstanding problems of heterogeneous catalysis that are identified in this paper will be investigated. For this purpose the paper is divided into several sections. The brief Introduction to the methodology and recent results of the surface science of heterogeneous catalysis is followed by a review of the concepts of heterogeneous catalysis. Then, the experimental results that identified the three molecular ingredients of catalysis, structure, carbonaceous deposit and the oxidation state of surface atoms are described. Each section is closed with a summary and a list of problems that require theoretical and experimental scrutiny. Finally attempts to build new catalyst systems and the theoretical and experimental problems that appeared in the course of this research are described.

Plasma-assisted heterogeneous catalysis for NOx reduction in lean-burn engine exhaust

Energy Technology Data Exchange (ETDEWEB)

Penetrante, B.M.; Hsaio, M.C.; Merritt, B.T.; Vogtlin, G.E. [Lawrence Livermore National Lab., CA (United States); Wan, C.Z.; Rice, G.W.; Voss, K.E. [Engelhard Corp., Iselin, NJ (United States)

1997-12-31

This paper discusses the combination of a plasma with a catalyst to improve the reduction of NO{sub x} under lean-burn conditions. The authors have been investigating the effects of a plasma on the NO{sub x} reduction activity and temperature operating window of various catalytic materials. One of the goals is to develop a fundamental understanding of the interaction between the gas-phase plasma chemistry and the heterogeneous chemistry on the catalyst surface. The authors have observed that plasma assisted heterogeneous catalysis can facilitate NO{sub x} reduction under conditions that normally make it difficult for either the plasma or the catalyst to function by itself. By systematically varying the plasma electrode and catalyst configuration, they have been able to elucidate the process by which the plasma chemistry affects the chemical reduction of NO{sub x} on the catalyst surface. They have discovered that the main effect of the plasma is to induce the gas-phase oxidation of NO to NO{sub 21}. The reduction of NO{sub x} to N{sub 2} is then accomplished by heterogeneous reaction of O with activated hydrocarbons on the catalyst surface. The use of a plasma opens the opportunity for a new class of catalysts that are potentially more durable, more active, more selective and more sulfur-tolerant compared to conventional lean-NO{sub x} catalysts.

Bridging Models and Business: Understanding heterogeneity in hidden drivers of customer purchase behavior

NARCIS (Netherlands)

E. Korkmaz (Evsen)

2014-01-01

markdownabstract__Abstract__ Recent years have seen many advances in quantitative models in the marketing literature. Even though these advances enable model building for a better understanding of customer purchase behavior and customer heterogeneity such that firms develop optimal targeting and

Development of a fluidized bed agglomeration modeling methodology to include particle-level heterogeneities in ash chemistry and granular physics

Science.gov (United States)

Khadilkar, Aditi B.

The utility of fluidized bed reactors for combustion and gasification can be enhanced if operational issues such as agglomeration are mitigated. The monetary and efficiency losses could be avoided through a mechanistic understanding of the agglomeration process and prediction of operational conditions that promote agglomeration. Pilot-scale experimentation prior to operation for each specific condition can be cumbersome and expensive. So the development of a mathematical model would aid predictions. With this motivation, the study comprised of the following model development stages- 1) development of an agglomeration modeling methodology based on binary particle collisions, 2) study of heterogeneities in ash chemical composition and gaseous atmosphere, 3) computation of a distribution of particle collision frequencies based on granular physics for a poly-disperse particle size distribution, 4) combining the ash chemistry and granular physics inputs to obtain agglomerate growth probabilities and 5) validation of the modeling methodology. The modeling methodology comprised of testing every binary particle collision in the system for sticking, based on the extent of dissipation of the particles' kinetic energy through viscous dissipation by slag-liquid (molten ash) covering the particles. In the modeling methodology developed in this study, thermodynamic equilibrium calculations are used to estimate the amount of slag-liquid in the system, and the changes in particle collision frequencies are accounted for by continuously tracking the number density of the various particle sizes. In this study, the heterogeneities in chemical composition of fuel ash were studied by separating the bulk fuel into particle classes that are rich in specific minerals. FactSage simulations were performed on two bituminous coals and an anthracite to understand the effect of particle-level heterogeneities on agglomeration. The mineral matter behavior of these constituent classes was studied

Understanding the Executive Functioning Heterogeneity in Schizophrenia

Science.gov (United States)

Raffard, Stephane; Bayard, Sophie

2012-01-01

Schizophrenia is characterized by heterogeneous brain abnormalities involving cerebral regions implied in the executive functioning. The dysexecutive syndrome is one of the most prominent and functionally cognitive features of schizophrenia. Nevertheless, it is not clear to what extend executive deficits are heterogeneous in schizophrenia…

Students' Energy Understanding Across Biology, Chemistry, and Physics Contexts

Science.gov (United States)

Opitz, S. T.; Neumann, K.; Bernholt, S.; Harms, U.

2017-07-01

Energy is considered both as a disciplinary core idea and as a concept cutting across science disciplines. Most previous approaches studied progressing energy understanding in specific disciplinary contexts, while disregarding the relation of understanding across them. Hence, this study provides a systematic analysis of cross-disciplinary energy learning. On the basis of a cross-sectional study with n = 742 students from grades 6, 8, and 10, we analyze students' progression in understanding energy across biology, chemistry, and physics contexts. The study is guided by three hypothetical scenarios that describe how the connection between energy understanding in the three disciplinary contexts changes across grade levels. These scenarios are compared using confirmatory factor analysis (CFA). The results suggest that, from grade 6 to grade 10, energy understanding in the three disciplinary contexts is highly interrelated, thus indicating a parallel progression of energy understanding in the three disciplinary contexts. In our study, students from grade 6 onwards appeared to have few problems to apply one energy understanding across the three disciplinary contexts. These findings were unexpected, as previous research concluded that students likely face difficulties in connecting energy learning across disciplinary boundaries. Potential reasons for these results and the characteristics of the observed cross-disciplinary energy understanding are discussed in the light of earlier findings and implications for future research, and the teaching of energy as a core idea and a crosscutting concept are addressed.

Using Mathematical Software to Introduce Fourier Transforms in Physical Chemistry to Develop Improved Understanding of Their Applications in Analytical Chemistry

Science.gov (United States)

Miller, Tierney C.; Richardson, John N.; Kegerreis, Jeb S.

2016-01-01

This manuscript presents an exercise that utilizes mathematical software to explore Fourier transforms in the context of model quantum mechanical systems, thus providing a deeper mathematical understanding of relevant information often introduced and treated as a "black-box" in analytical chemistry courses. The exercise is given to…

Ion binding by humic and fulvic acids: A computational procedure based on functional site heterogeneity and the physical chemistry of polyelectrolyte solutions

International Nuclear Information System (INIS)

Marinsky, J.A.; Reddy, M.M.; Ephraim, J.; Mathuthu, A.

1988-04-01

Ion binding equilibria for humic and fulvic acids are examined from the point of view of functional site heterogeneity and the physical chemistry of polyelectrolyte solutions. A detailed explanation of the potentiometric properties of synthetic polyelectrolytes and ion-exchange gels is presented first to provide the basis for a parallel consideration of the potentiometric properties exhibited by humic and fulvic acids. The treatment is then extended to account for functional site heterogeneity. Sample results are presented for analysis of the ion-binding reactions of a standard soil fulvic acid (Armadale Horizons Bh) with this approach to test its capability for anticipation of metal ion removal from solution. The ultimate refined model is shown to be adaptable, after appropriate consideration of the heterogeneity and polyelectrolyte factors, to programming already available for the consideration of ion binding by inorganics in natural waters. (orig.)

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

Science.gov (United States)

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…

Understanding the Impact of a General Chemistry Course on Students' Transition to Organic Chemistry

Science.gov (United States)

Collins-Webb, Alexandra; Jeffery, Kathleen A.; Sweeder, Ryan D.

2016-01-01

The move from general chemistry to organic chemistry can be a challenge for students as it often involves a transition from quantitatively-oriented to mechanistically-oriented thinking. This study found that the design of the general chemistry course can change the student experience of this transition as assessed by a reflective survey. The…

Understanding Interdependencies between Heterogeneous Earth Observation Systems When Applied to Federal Objectives

Science.gov (United States)

Gallo, J.; Sylak-Glassman, E.

2017-12-01

We will present a method for assessing interdependencies between heterogeneous Earth observation (EO) systems when applied to key Federal objectives. Using data from the National Earth Observation Assessment (EOA), we present a case study that examines the frequency that measurements from each of the Landsat 8 sensors are used in conjunction with heterogeneous measurements from other Earth observation sensors to develop data and information products. This EOA data allows us to map the most frequent interactions between Landsat measurements and measurements from other sensors, identify high-impact data and information products where these interdependencies occur, and identify where these combined measurements contribute most to meeting a key Federal objective within one of the 13 Societal Benefit Areas used in the EOA study. Using a value-tree framework to trace the application of data from EO systems to weighted key Federal objectives within the EOA study, we are able to estimate relative contribution of individual EO systems to meeting those objectives, as well as the interdependencies between measurements from all EO systems within the EOA study. The analysis relies on a modified Delphi method to elicit relative levels of reliance on individual measurements from EO systems, including combinations of measurements, from subject matter experts. This results in the identification of a representative portfolio of all EO systems used to meet key Federal objectives. Understanding the interdependencies among a heterogeneous set of measurements that modify the impact of any one individual measurement on meeting a key Federal objective, especially if the measurements originate from multiple agencies or state/local/tribal, international, academic, and commercial sources, can impact agency decision-making regarding mission requirements and inform understanding of user needs.

Gas-surface interactions and heterogeneous chemistry on interstellar grains analogues

Directory of Open Access Journals (Sweden)

Cazaux S.

2012-01-01

Full Text Available Detailed laboratory studies and progress in surface science technique, have allowed in recent years the first experimental confirmation of surface reaction schemes, as introduced by Tielens, Hagen and Charnley [1,2]. In this paper, we review few heterogeneous processes which give routes to form elementary molecules considered as precursors for explaining the variety and richness of molecular species in the interstellar medium. Adsorption, diffusion and reaction processes are discussed. With emphasis on the experimental approaches, but also supported by theoretical developments, progresses in the understanding of the “catalytic role” of a dust grain surface in various physical conditions are described. Recent advances made on few important species (H2, H2O, CH3OH are used to illustrate basic properties and raise open questions.

Meaningful Understanding and Systems Thinking in Organic Chemistry: Validating Measurement and Exploring Relationships

Science.gov (United States)

Vachliotis, Theodoros; Salta, Katerina; Tzougraki, Chryssa

2014-01-01

The purpose of this study was dual: First, to develop and validate assessment schemes for assessing 11th grade students' meaningful understanding of organic chemistry concepts, as well as their systems thinking skills in the domain. Second, to explore the relationship between the two constructs of interest based on students' performance…

Heterogeneous continuous-time random walks

Science.gov (United States)

Grebenkov, Denis S.; Tupikina, Liubov

2018-01-01

We introduce a heterogeneous continuous-time random walk (HCTRW) model as a versatile analytical formalism for studying and modeling diffusion processes in heterogeneous structures, such as porous or disordered media, multiscale or crowded environments, weighted graphs or networks. We derive the exact form of the propagator and investigate the effects of spatiotemporal heterogeneities onto the diffusive dynamics via the spectral properties of the generalized transition matrix. In particular, we show how the distribution of first-passage times changes due to local and global heterogeneities of the medium. The HCTRW formalism offers a unified mathematical language to address various diffusion-reaction problems, with numerous applications in material sciences, physics, chemistry, biology, and social sciences.

Heterogeneous catalysis: on bathroom mirrors and boiling stones

NARCIS (Netherlands)

Philipse, A.P.

2011-01-01

A catalyst is defined as a substance that accelerates a process without undergoing a net change due to that process. Most chemistry students learn about catalysts in the context of chemical reactions, such as the enzymes in biochemistry or the heterogeneous metal catalysts in inorganic chemistry (1,

Virtual Laboratory in the Role of Dynamic Visualisation for Better Understanding of Chemistry in Primary School

Science.gov (United States)

Herga, Nataša Rizman; Cagran, Branka; Dinevski, Dejan

2016-01-01

Understanding chemistry includes the ability to think on three levels: the macroscopic level, the symbolic level, and the level of particles--sub-microscopic level. Pupils have the most difficulty when trying to understand the sub-microscopic level because it is outside their range of experience. A virtual laboratory enables a simultaneous…

Toward Understanding the Heterogeneity in OCD: Evidence from narratives in adult patients

Science.gov (United States)

Van Schalkwyk, Gerrit I; Bhalla, Ish P; Griepp, Matthew; Kelmendi, Benjamin; Davidson, Larry; Pittenger, Christopher

2015-01-01

Background Current attempts at understanding the heterogeneity in OCD have relied on quantitative methods. The results of such work point towards a dimensional structure for OCD. Existing qualitative work in OCD has focused on understanding specific aspects of the OCD experience in greater depth. However, qualitative methods are also of potential value in furthering our understanding of OCD heterogeneity by allowing for open-ended exploration of the OCD experience and correlating identified subtypes with patient narratives. Aims We explored variations in patients’ experience prior to, during, and immediately after performing their compulsions. Method Semi-structured interviews were conducted with 20 adults with OCD, followed by inductive thematic analysis. Participant responses were not analyzed within the context of an existing theoretical framework, and themes were labeled descriptively. Results The previously dichotomy of ‘anxiety’ vs ‘incompleteness’ emerged organically during narrative analysis. In addition, we found that some individuals with OCD utilize their behaviors as a way to cope with stress and anxiety more generally. Other participants did not share this experience and denied finding any comfort in their OC behaviors. The consequences of attention difficulties were highlighted, with some participants describing how difficulty focusing on a task could influence the need for it to be repeated multiple times. Conclusions The extent to which patients use OCD as a coping mechanism is a relevant distinction with potential implications for treatment engagement. Patients may experience ambivalence about suppressing behaviors that they have come to rely upon for management of stress and anxiety, even if these behaviors represent symptoms of a psychiatric illness. PMID:25855685

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

Science.gov (United States)

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…

Understanding Heterogeneous Preferences of Cooperative Members

NARCIS (Netherlands)

Kalogeras, N.; Pennings, J.M.E.; Lans, van der I.A.; Garcia, P.; Dijk, van G.

2009-01-01

We study the heterogeneity in the preference structure of cooperative members. Using conjoint analysis the utility that members attach to intra-organizational and strategic attributes of their cooperative is elicited. Recognizing that members are not homogenous, a concomitant finitemixture

Advances in electron transfer chemistry

CERN Document Server

Mariano, Patrick S

1993-01-01

Advances in Electron Transfer Chemistry, Volume 3 presents studies that discuss findings in the various aspects of electron chemistry. The book is comprised of four chapters; each chapter reviews a work that tackles an issue in electron transfer chemistry. Chapter 1 discusses the photoinduced electron transfer in flexible biaryl donor-acceptor molecules. Chapter 2 tackles light-induced electron transfer in inorganic systems in homogeneous and heterogeneous phases. The book also covers internal geometry relaxation effects on electron transfer rates of amino-centered systems. The sequential elec

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

Science.gov (United States)

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…

Development and Analysis of an Instrument to Assess Student Understanding of GOB Chemistry Knowledge Relevant to Clinical Nursing Practice

Science.gov (United States)

Brown, Corina E.; Hyslop, Richard M.; Barbera, Jack

2015-01-01

The General, Organic, and Biological Chemistry Knowledge Assessment (GOB-CKA) is a multiple-choice instrument designed to assess students' understanding of the chemistry topics deemed important to clinical nursing practice. This manuscript describes the development process of the individual items along with a psychometric evaluation of the…

Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials: A review.

Science.gov (United States)

He, Jie; Yang, Xiaofang; Men, Bin; Wang, Dongsheng

2016-01-01

The heterogeneous Fenton reaction can generate highly reactive hydroxyl radicals (OH) from reactions between recyclable solid catalysts and H2O2 at acidic or even circumneutral pH. Hence, it can effectively oxidize refractory organics in water or soils and has become a promising environmentally friendly treatment technology. Due to the complex reaction system, the mechanism behind heterogeneous Fenton reactions remains unresolved but fascinating, and is crucial for understanding Fenton chemistry and the development and application of efficient heterogeneous Fenton technologies. Iron-based materials usually possess high catalytic activity, low cost, negligible toxicity and easy recovery, and are a superior type of heterogeneous Fenton catalysts. Therefore, this article reviews the fundamental but important interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials. OH, hydroperoxyl radicals/superoxide anions (HO2/O2(-)) and high-valent iron are the three main types of reactive oxygen species (ROS), with different oxidation reactivity and selectivity. Based on the mechanisms of ROS generation, the interfacial mechanisms of heterogeneous Fenton systems can be classified as the homogeneous Fenton mechanism induced by surface-leached iron, the heterogeneous catalysis mechanism, and the heterogeneous reaction-induced homogeneous mechanism. Different heterogeneous Fenton systems catalyzed by characteristic iron-based materials are comprehensively reviewed. Finally, related future research directions are also suggested. Copyright © 2015. Published by Elsevier B.V.

Improving Students' Understanding of Molecular Structure through Broad-Based Use of Computer Models in the Undergraduate Organic Chemistry Lecture

Science.gov (United States)

Springer, Michael T.

2014-01-01

Several articles suggest how to incorporate computer models into the organic chemistry laboratory, but relatively few papers discuss how to incorporate these models broadly into the organic chemistry lecture. Previous research has suggested that "manipulating" physical or computer models enhances student understanding; this study…

Real-Time Monitoring of Heterogeneous Catalysis with Mass Spectrometry

Science.gov (United States)

Young, Mark A.

2009-01-01

Heterogeneous, gas-solid processes constitute an important class of catalytic reactions that play a key role in a variety of applications, such as industrial processing and environmental controls. Heterogeneous catalytic chemistry can be demonstrated in a simple heated flow reactor containing a fragment of the catalytic converter from a vehicular…

Comprehensive understanding of mole concept subject matter according to the tetrahedral chemistry education (empirical study on the first-year chemistry students of Technische Universität Dresden)

Science.gov (United States)

Prabowo, D. W.; Mulyani, S.; van Pée, K.-H.; Indriyanti, N. Y.

2018-05-01

This research aims to apprehend: (1) the shape of tetrahedral chemistry education which is called the future of chemistry education, (2) comprehensive understanding of chemistry first-year students of Technische Universität Dresden according to the chemistry education’s tetrahedral shape on mole concept subject matter. This research used quantitative and qualitative; paper and pencil test and interview. The former was conducted in the form of test containing objective test instrument. The results of this study are (1) learning based on tetrahedral shape of chemistry education put the chemical substance (macroscopic), symbolic representation (symbol), and its process (molecular) in the context of human beings (human element) by integrating content and context, without emphasis on one thing and weaken another, (2) first-year chemistry students of Technische Universität Dresden have comprehensively understood the mole concept associated with the context of everyday life, whereby students are able to find out macroscopic information from statements that are contextual to human life and then by using symbols and formulas are able to comprehend the molecular components as well as to interpret and analyse problems effectively.

Simulation of stratospheric water vapor trends: impact on stratospheric ozone chemistry

Directory of Open Access Journals (Sweden)

A. Stenke

2005-01-01

Full Text Available A transient model simulation of the 40-year time period 1960 to 1999 with the coupled climate-chemistry model (CCM ECHAM4.L39(DLR/CHEM shows a stratospheric water vapor increase over the last two decades of 0.7 ppmv and, additionally, a short-term increase after major volcanic eruptions. Furthermore, a long-term decrease in global total ozone as well as a short-term ozone decline in the tropics after volcanic eruptions are modeled. In order to understand the resulting effects of the water vapor changes on lower stratospheric ozone chemistry, different perturbation simulations were performed with the CCM ECHAM4.L39(DLR/CHEM feeding the water vapor perturbations only to the chemistry part. Two different long-term perturbations of lower stratospheric water vapor, +1 ppmv and +5 ppmv, and a short-term perturbation of +2 ppmv with an e-folding time of two months were applied. An additional stratospheric water vapor amount of 1 ppmv results in a 5–10% OH increase in the tropical lower stratosphere between 100 and 30 hPa. As a direct consequence of the OH increase the ozone destruction by the HOx cycle becomes 6.4% more effective. Coupling processes between the HOx-family and the NOx/ClOx-family also affect the ozone destruction by other catalytic reaction cycles. The NOx cycle becomes 1.6% less effective, whereas the effectiveness of the ClOx cycle is again slightly enhanced. A long-term water vapor increase does not only affect gas-phase chemistry, but also heterogeneous ozone chemistry in polar regions. The model results indicate an enhanced heterogeneous ozone depletion during antarctic spring due to a longer PSC existence period. In contrast, PSC formation in the northern hemisphere polar vortex and therefore heterogeneous ozone depletion during arctic spring are not affected by the water vapor increase, because of the less PSC activity. Finally, this study shows that 10% of the global total ozone decline in the transient model run

Chemistry Division: Annual progress report for period ending March 31, 1987

International Nuclear Information System (INIS)

1987-08-01

This report is divided into the following sections: coal chemistry; aqueous chemistry at high temperatures and pressures; geochemistry of crustal processes to high temperatures and pressures; chemistry of advanced inorganic materials; structure and dynamics of advanced polymeric materials; chemistry of transuranium elements and compounds; separations chemistry; reactions and catalysis in molten salts; surface science related to heterogeneous catalysis; electron spectroscopy; chemistry related to nuclear waste disposal; computational modeling of security document printing; and special topics

Understanding intratumor heterogeneity by combining genome analysis and mathematical modeling.

Science.gov (United States)

Niida, Atsushi; Nagayama, Satoshi; Miyano, Satoru; Mimori, Koshi

2018-04-01

Cancer is composed of multiple cell populations with different genomes. This phenomenon called intratumor heterogeneity (ITH) is supposed to be a fundamental cause of therapeutic failure. Therefore, its principle-level understanding is a clinically important issue. To achieve this goal, an interdisciplinary approach combining genome analysis and mathematical modeling is essential. For example, we have recently performed multiregion sequencing to unveil extensive ITH in colorectal cancer. Moreover, by employing mathematical modeling of cancer evolution, we demonstrated that it is possible that this ITH is generated by neutral evolution. In this review, we introduce recent advances in a research field related to ITH and also discuss strategies for exploiting novel findings on ITH in a clinical setting. © 2018 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.

Improving Understanding of Spatial Heterogeneity in Mountain Ecohydrology with Multispectral Unmanned Aerial Systems (UAS).

Science.gov (United States)

Wigmore, O.; Molotch, N. P.

2017-12-01

Mountain regions are a critical component of the hydrologic system. These regions are extremely heterogeneous, with dramatic topographic, climatic, ecologic and hydrologic variations occurring over very short distances. This heterogeneity makes understanding changes in these environments difficult. Commonly used satellite data are often too coarse to resolve processes at appropriate scales and point measurements are typically unrepresentative of the wider region. The rapid rise of Unmanned Aerial Systems (UAS) offers a potential solution to the scale-related inadequacies of satellite and ground-based observing systems. Using UAS, spatially distributed datasets can be collected at high resolution (i.e. cm), on demand, and can therefore facilitate improved understanding of mountain ecohydrology. We deployed a custom built multispectral - visible (RGB), near infrared (NIR) and thermal infrared (TIR) - UAS at a weekly interval over the Niwot Ridge Long Term Ecological Research (NWT LTER) saddle catchment at 3500masl in the Colorado Rockies. This system was used to map surface water pathways, land cover and topography, and quantify ecohydrologic variables including, snow depth, vegetation productivity and surface soil moisture at 5-50cm resolution across an 80ha study area. This presentation will discuss the techniques, methods and merits of using UAS derived multispectral data for ecohydrologic research in mountain regions. We will also present preliminary findings from our survey time series at NWT LTER and a discussion of the potential insights that these datasets can provide. Key questions to be addressed are: 1) how does spatial variability in snow depth impact soil moisture and vegetation productivity, 2) how can UAS help us to identify ecohydrologic `hotspots' and `hot moments' across heterogeneous landscapes.

Identification of Misconceptions through Multiple Choice Tasks at Municipal Chemistry Competition Test

Directory of Open Access Journals (Sweden)

Dušica D Milenković

2016-01-01

Full Text Available In this paper, the level of conceptual understanding of chemical contents among seventh grade students who participated in the municipal Chemistry competition in Novi Sad, Serbia, in 2013 have been examined. Tests for the municipal chemistry competition were used as a measuring instrument, wherein only multiple choice tasks were considered and analyzed. Determination of the level of conceptual understanding of the tested chemical contents was based on the calculation of the frequency of choosing the correct answers. Thereby, identification of areas of satisfactory conceptual understanding, areas of roughly adequate performance, areas of inadequate performance, and areas of quite inadequate performance have been conducted. On the other hand, the analysis of misconceptions was based on the analysis of distractors. The results showed that satisfactory level of conceptual understanding and roughly adequate performance characterize majority of contents, which was expected since only the best students who took part in the contest were surveyed. However, this analysis identified a large number of misunderstandings, as well. In most of the cases, these misconceptions were related to the inability to distinguish elements, compounds, homogeneous and heterogeneous mixtures. Besides, it is shown that students are not familiar with crystal structure of the diamond, and with metric prefixes. The obtained results indicate insufficient visualization of the submicroscopic level in school textbooks, the imprecise use of chemical language by teachers and imprecise use of language in chemistry textbooks.

Genetic heterogeneity of retinitis pigmentosa

OpenAIRE

Hartono, Hartono

2015-01-01

Genetic heterogeneity is a phenomenon in which a genetic disease can be transmitted by several modes of inheritance. The understanding of genetic heterogeneity is important in giving genetic counselling.The presence of genetic heterogeneity can be explained by the existence of:1.different mutant alleles at a single locus, and2.mutant alleles at different loci affecting the same enzyme or protein, or affecting different enzymes or proteins.To have an overall understanding of genetic heterogene...

Chemistry Division: Annual progress report for period ending March 31, 1987

Energy Technology Data Exchange (ETDEWEB)

1987-08-01

This report is divided into the following sections: coal chemistry; aqueous chemistry at high temperatures and pressures; geochemistry of crustal processes to high temperatures and pressures; chemistry of advanced inorganic materials; structure and dynamics of advanced polymeric materials; chemistry of transuranium elements and compounds; separations chemistry; reactions and catalysis in molten salts; surface science related to heterogeneous catalysis; electron spectroscopy; chemistry related to nuclear waste disposal; computational modeling of security document printing; and special topics. (DLC)

The physical chemistry and materials science behind sinter-resistant catalysts.

Science.gov (United States)

Dai, Yunqian; Lu, Ping; Cao, Zhenming; Campbell, Charles T; Xia, Younan

2018-06-18

Catalyst sintering, a main cause of the loss of catalytic activity and/or selectivity at high reaction temperatures, is a major concern and grand challenge in the general area of heterogeneous catalysis. Although all heterogeneous catalysts are inevitably subjected to sintering during their operation, the immediate and drastic consequences can be mitigated by carefully engineering the catalytic particles and their interactions with the supports. In this tutorial review, we highlight recent progress in understanding the physical chemistry and materials science involved in sintering, including the discussion of advanced techniques, such as in situ microscopy and spectroscopy, for investigating the sintering process and its rate. We also discuss strategies for the design and rational fabrication of sinter-resistant catalysts. Finally, we showcase recent success in improving the thermal stability and thus sinter resistance of supported catalytic systems.

Understanding premixed flame chemistry of gasoline fuels by comparing quantities of interest

KAUST Repository

Selim, Hatem

2016-07-23

Gasoline fuels are complex mixtures that vary in composition depending on crude oil feedstocks and refining processes. Gasoline combustion in high-speed spark ignition engines is governed by flame propagation, so understanding fuel composition effects on premixed flame chemistry is important. In this study, the combustion chemistry of low-pressure, burner-stabilized, premixed flames of two gasoline fuels was investigated under stoichiometric conditions. Flame speciation was conducted using vacuum-ultraviolet synchrotron photoionization time-of-flight molecular beam mass spectroscopy. Stable end-products, intermediate hydrocarbons, and free radicals were detected and quantified. In addition, several isomeric species in the reaction pool were distinguished and quantified with the help of the highly tunable synchrotron radiation. A comparison between the products of both flames is presented and the major differences are highlighted. Premixed flame numerical simulations were conducted using surrogate fuel kinetic models for each flame. Furthermore, a new approach was developed to elucidate the main discrepancies between experimental measurements and the numerical predictions by comparing quantities of interest. © 2016.

Industrial applications of radiation chemistry

International Nuclear Information System (INIS)

Puig, Jean Rene

1959-01-01

The status of industrial applications of radiation chemistry as it stands 6 months after the second Geneva international conference is described. The main features of the interaction of ionizing radiations with matter are briefly stated and a review is made of the best studied and the more promising systems of radiation chemistry. The fields of organics, plastics, heterogeneous catalysis are emphasized. Economies of radiation production and utilization are discussed. Reprint of a paper published in Industries atomiques - no. 5-6, 1959

Impact of aircraft emissions on the atmospheric chemistry

Energy Technology Data Exchange (ETDEWEB)

Dameris, M; Sausen, R; Grewe, V; Koehler, I; Ponater, M [Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt e.V., Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere; Steil, B [Max-Planck-Inst. fuer Meteorologie, Hamburg (Germany); Bruehl, Ch [Max-Planck-Inst. fuer Chemie (Otto-Hahn-Institut), Mainz (Germany)

1998-12-31

A hierarchy of models of different complexity has been applied to estimate the impact of aircraft NO{sub x} emissions on atmospheric chemistry. The global circulation model ECHAM3 has been coupled with two types of chemistry modules. The first of these describes only a simplified (linear) NO{sub x} and HNO{sub 3} chemistry while the second one is a comprehensive chemistry module (CHEM), describing tropospheric and stratospheric chemistry including photochemical reactions and heterogeneous reactions on sulphate aerosols and PSCs. The module CHEM has been coupled either off-line or with feedback via the ozone concentration. First results of multilayer integrations (over decades) are discussed. (author) 27 refs.

Impact of aircraft emissions on the atmospheric chemistry

Energy Technology Data Exchange (ETDEWEB)

Dameris, M.; Sausen, R.; Grewe, V.; Koehler, I.; Ponater, M. [Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt e.V., Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere; Steil, B. [Max-Planck-Inst. fuer Meteorologie, Hamburg (Germany); Bruehl, Ch. [Max-Planck-Inst. fuer Chemie (Otto-Hahn-Institut), Mainz (Germany)

1997-12-31

A hierarchy of models of different complexity has been applied to estimate the impact of aircraft NO{sub x} emissions on atmospheric chemistry. The global circulation model ECHAM3 has been coupled with two types of chemistry modules. The first of these describes only a simplified (linear) NO{sub x} and HNO{sub 3} chemistry while the second one is a comprehensive chemistry module (CHEM), describing tropospheric and stratospheric chemistry including photochemical reactions and heterogeneous reactions on sulphate aerosols and PSCs. The module CHEM has been coupled either off-line or with feedback via the ozone concentration. First results of multilayer integrations (over decades) are discussed. (author) 27 refs.

Mixing-controlled uncertainty in long-term predictions of acid rock drainage from heterogeneous waste-rock piles

Science.gov (United States)

Pedretti, D.; Beckie, R. D.; Mayer, K. U.

2015-12-01

The chemistry of drainage from waste-rock piles at mine sites is difficult to predict because of a number of uncertainties including heterogeneous reactive mineral content, distribution of minerals, weathering rates and physical flow properties. In this presentation, we examine the effects of mixing on drainage chemistry over timescales of 100s of years. We use a 1-D streamtube conceptualization of flow in waste rocks and multicomponent reactive transport modeling. We simplify the reactive system to consist of acid-producing sulfide minerals and acid-neutralizing carbonate minerals and secondary sulfate and iron oxide minerals. We create multiple realizations of waste-rock piles with distinct distributions of reactive minerals along each flow path and examine the uncertainty of drainage geochemistry through time. The limited mixing of streamtubes that is characteristic of the vertical unsaturated flow in many waste-rock piles, allows individual flowpaths to sustain acid or neutral conditions to the base of the pile, where the streamtubes mix. Consequently, mixing and the acidity/alkalinity balance of the streamtube waters, and not the overall acid- and base-producing mineral contents, control the instantaneous discharge chemistry. Our results show that the limited mixing implied by preferential flow and the heterogeneous distribution of mineral contents lead to large uncertainty in drainage chemistry over short and medium time scales. However, over longer timescales when one of either the acid-producing or neutralizing primary phases is depleted, the drainage chemistry becomes less controlled by mixing and in turn less uncertain. A correct understanding of the temporal variability of uncertainty is key to make informed long-term decisions in mining settings regarding the management of waste material.

Is Chemistry Attractive for Pupils? Czech Pupils' Perception of Chemistry

Science.gov (United States)

Kubiatko, Milan

2015-01-01

Chemistry is an important subject due to understanding the composition and structure of the things around us. The main aim of the study was to find out the perception of chemistry by lower secondary school pupils. The partial aims were to find out the influence of gender, year of study and favorite subject on the perception of chemistry. The…

Understanding the Role of Water on Electron-Initiated Processes and Radical Chemistry

Energy Technology Data Exchange (ETDEWEB)

Garrett, Bruce C [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Colson, Steven D [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dixon, David A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Laufer, Allan H [US Department of Energy Office of Science Office of Basic Energy Sciences; Ray, Douglas [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2003-06-10

On September 26–28, 2002, a workshop entitled “Understanding the Role of Water on Electron-Initiated Processes and Radical Chemistry” was held to assess new research opportunities in electron-driven processes and radical chemistry in aqueous systems. Of particular interest was the unique and complex role that the structure of water plays in influencing these processes. Novel experimental and theoretical approaches to solving long-standing problems in the field were explored. A broad selection of participants from universities and the national laboratories contributed to the workshop, which included scientific and technical presentations and parallel sessions for discussions and report writing.

Sepsis: Multiple Abnormalities, Heterogeneous Responses, and Evolving Understanding

Science.gov (United States)

Iskander, Kendra N.; Osuchowski, Marcin F.; Stearns-Kurosawa, Deborah J.; Kurosawa, Shinichiro; Stepien, David; Valentine, Catherine

2013-01-01

Sepsis represents the host's systemic inflammatory response to a severe infection. It causes substantial human morbidity resulting in hundreds of thousands of deaths each year. Despite decades of intense research, the basic mechanisms still remain elusive. In either experimental animal models of sepsis or human patients, there are substantial physiological changes, many of which may result in subsequent organ injury. Variations in age, gender, and medical comorbidities including diabetes and renal failure create additional complexity that influence the outcomes in septic patients. Specific system-based alterations, such as the coagulopathy observed in sepsis, offer both potential insight and possible therapeutic targets. Intracellular stress induces changes in the endoplasmic reticulum yielding misfolded proteins that contribute to the underlying pathophysiological changes. With these multiple changes it is difficult to precisely classify an individual's response in sepsis as proinflammatory or immunosuppressed. This heterogeneity also may explain why most therapeutic interventions have not improved survival. Given the complexity of sepsis, biomarkers and mathematical models offer potential guidance once they have been carefully validated. This review discusses each of these important factors to provide a framework for understanding the complex and current challenges of managing the septic patient. Clinical trial failures and the therapeutic interventions that have proven successful are also discussed. PMID:23899564

Bibliography of Work on the Heterogeneous Photocatalytic Removal of Hazardous Compounds from Water

Energy Technology Data Exchange (ETDEWEB)

Blake, D. M.

1999-07-29

The subject of this report is chemistry and engineering for the application of heterogeneous photocatalysts. The state of the art in catalysts are forms of titanium dioxide or modifications thereof, but work on other heterogeneous catalysts is included.

Operando research in heterogeneous catalysis

CERN Document Server

Groot, Irene

2017-01-01

This book is devoted to the emerging field of techniques for visualizing atomic-scale properties of active catalysts under actual working conditions, i.e. high gas pressures and high temperatures. It explains how to understand these observations in terms of the surface structures and dynamics and their detailed interplay with the gas phase. This provides an important new link between fundamental surface physics and chemistry, and applied catalysis. The book explains the motivation and the necessity of operando studies, and positions these with respect to the more traditional low-pressure investigations on the one hand and the reality of industrial catalysis on the other. The last decade has witnessed a rapid development of new experimental and theoretical tools for operando studies of heterogeneous catalysis. The book has a strong emphasis on the new techniques and illustrates how the challenges introduced by the harsh, operando conditions are faced for each of these new tools. Therefore, one can also read th...

Chemistry in aircraft plumes

Energy Technology Data Exchange (ETDEWEB)

Kraabol, A.G.; Stordal, F.; Knudsen, S. [Norwegian Inst. for Air Research, Kjeller (Norway); Konopka, P. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

1997-12-31

An expanding plume model with chemistry has been used to study the chemical conversion of NO{sub x} to reservoir species in aircraft plumes. The heterogeneous conversion of N{sub 2}O{sub 5} to HNO{sub 3}(s) has been investigated when the emissions take place during night-time. The plume from an B747 has been simulated. During a ten-hour calculation the most important reservoir species was HNO{sub 3} for emissions at noon. The heterogeneous reactions had little impact on the chemical loss of NO{sub x} to reservoir species for emissions at night. (author) 4 refs.

Chemistry in aircraft plumes

Energy Technology Data Exchange (ETDEWEB)

Kraabol, A G; Stordal, F; Knudsen, S [Norwegian Inst. for Air Research, Kjeller (Norway); Konopka, P [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

1998-12-31

An expanding plume model with chemistry has been used to study the chemical conversion of NO{sub x} to reservoir species in aircraft plumes. The heterogeneous conversion of N{sub 2}O{sub 5} to HNO{sub 3}(s) has been investigated when the emissions take place during night-time. The plume from an B747 has been simulated. During a ten-hour calculation the most important reservoir species was HNO{sub 3} for emissions at noon. The heterogeneous reactions had little impact on the chemical loss of NO{sub x} to reservoir species for emissions at night. (author) 4 refs.

Liquid Structure with Nano-Heterogeneity Promotes Cationic Transport in Concentrated Electrolytes.

Science.gov (United States)

Borodin, Oleg; Suo, Liumin; Gobet, Mallory; Ren, Xiaoming; Wang, Fei; Faraone, Antonio; Peng, Jing; Olguin, Marco; Schroeder, Marshall; Ding, Michael S; Gobrogge, Eric; von Wald Cresce, Arthur; Munoz, Stephen; Dura, Joseph A; Greenbaum, Steve; Wang, Chunsheng; Xu, Kang

2017-10-24

Using molecular dynamics simulations, small-angle neutron scattering, and a variety of spectroscopic techniques, we evaluated the ion solvation and transport behaviors in aqueous electrolytes containing bis(trifluoromethanesulfonyl)imide. We discovered that, at high salt concentrations (from 10 to 21 mol/kg), a disproportion of cation solvation occurs, leading to a liquid structure of heterogeneous domains with a characteristic length scale of 1 to 2 nm. This unusual nano-heterogeneity effectively decouples cations from the Coulombic traps of anions and provides a 3D percolating lithium-water network, via which 40% of the lithium cations are liberated for fast ion transport even in concentration ranges traditionally considered too viscous. Due to such percolation networks, superconcentrated aqueous electrolytes are characterized by a high lithium-transference number (0.73), which is key to supporting an assortment of battery chemistries at high rate. The in-depth understanding of this transport mechanism establishes guiding principles to the tailored design of future superconcentrated electrolyte systems.

Environmental chemistry. Seventh edition

Energy Technology Data Exchange (ETDEWEB)

Manahan, S.E. [Univ. of Missouri, Columbia, MO (United States)

1999-11-01

This book presents a basic understanding of environmental chemistry and its applications. In addition to providing updated materials in this field, the book emphasizes the major concepts essential to the practice of environmental chemistry. Topics of discussion include the following: toxicological chemistry; toxicological chemistry of chemical substances; chemical analysis of water and wastewater; chemical analysis of wastes and solids; air and gas analysis; chemical analysis of biological materials and xenobiotics; fundamentals of chemistry; and fundamentals of organic chemistry.

The physical basis of chemistry

CERN Document Server

Warren, Warren S

2000-01-01

If the text you're using for general chemistry seems to lack sufficient mathematics and physics in its presentation of classical mechanics, molecular structure, and statistics, this complementary science series title may be just what you're looking for. Written for the advanced lower-division undergraduate chemistry course, The Physical Basis of Chemistry, Second Edition, offers students an opportunity to understand and enrich the understanding of physical chemistry with some quantum mechanics, the Boltzmann distribution, and spectroscopy. Posed and answered are questions concerning eve

Chemistry, Poetry, and Artistic Illustration: An Interdisciplinary Approach to Teaching and Promoting Chemistry

Science.gov (United States)

Furlan, Ping Y.; Kitson, Herbert; Andes, Cynthia

2007-10-01

This article describes a successful interdisciplinary collaboration among chemistry, humanities and English faculty members, who utilized poetry and artistic illustration to help students learn, appreciate, and enjoy chemistry. Students taking general chemistry classes were introduced to poetry writing and museum-type poster preparation during one class period. They were then encouraged to use their imagination and creativity to brainstorm and write chemistry poems or humors on the concepts and principles covered in the chemistry classes and artistically illustrate their original work on posters. The project, 2 3 months in length, was perceived by students as effective at helping them learn chemistry and express their understanding in a fun, personal, and creative way. The instructors found students listened to the directives because many posters were witty, clever, and eye-catching. They showed fresh use of language and revealed a good understanding of chemistry. The top posters were created by a mix of A-, B-, and C-level students. The fine art work, coupled with poetry, helped chemistry come alive on campus, providing an aesthetic presentation of materials that engaged the general viewer.

Building an Understanding of How Model-Based Inquiry Is Implemented in the High School Chemistry Classroom

Science.gov (United States)

Dass, Katarina; Head, Michelle L.; Rushton, Gregory T.

2015-01-01

Modeling as a scientific practice in K-12 classrooms has received a wealth of attention in the U.S. and abroad due to the advent of revised national science education standards. The study described herein investigated how a group of high school chemistry teachers developed their understanding of the nature and function of models in the precollege…

New trends and developments in radiation chemistry

International Nuclear Information System (INIS)

1989-10-01

Radiation chemistry is a branch of chemistry that studies chemical transformations in materials exposed to high-energy radiations. It uses radiation as the initiator of chemical reactions. Practical applications of radiation chemistry today extend to many fields, including health care, food and agriculture, manufacturing, industrial pollution abatement, biotechnology and telecommunications. The important advantage of radiation chemistry lies in its ability to be used to produce, and study, almost any reactive atomic and molecular species playing a part in chemical reactions, synthesis, industrial processes, or in biological systems. The techniques are applicable to gaseous, liquid, solid, and heterogeneous systems. By combining different techniques of radiation chemistry with analytical chemistry, the reaction mechanism and kinetics of chemical reactions are studied. In November 1988 in Bologna, Italy, the IAEA convened an advisory group meeting to assess new trends and developments in radiation chemistry. The present publication includes most of the contributions presented at the meeting. Refs, figs and tabs

Introducing Chemistry Students to the "Real World" of Chemistry

Science.gov (United States)

Brown, Michael E.; Cosser, Ronald C.; Davies-Coleman, Michael T.; Kaye, Perry T.; Klein, Rosalyn; Lamprecht, Emmanuel; Lobb, Kevin; Nyokong, Tebello; Sewry, Joyce D.; Tshentu, Zenixole R.; van der Zeyde, Tino; Watkins, Gareth M.

2010-01-01

A majority of chemistry graduates seek employment in a rapidly changing chemical industry. Our attempts to provide the graduates with skills in entrepreneurship and the ability to understand and communicate with their chemical engineering colleagues, in addition to their fundamental knowledge of chemistry, are described. This is done at…

Students' Understanding of Alkyl Halide Reactions in Undergraduate Organic Chemistry

Science.gov (United States)

Cruz-Ramirez de Arellano, Daniel

2013-01-01

Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is…

Chemistry Division annual progress report for period ending April 30, 1993

Energy Technology Data Exchange (ETDEWEB)

Poutsma, M.L.; Ferris, L.M.; Mesmer, R.E.

1993-08-01

The Chemistry Division conducts basic and applied chemical research on projects important to DOE`s missions in sciences, energy technologies, advanced materials, and waste management/environmental restoration; it also conducts complementary research for other sponsors. The research are arranged according to: coal chemistry, aqueous chemistry at high temperatures and pressures, geochemistry, chemistry of advanced inorganic materials, structure and dynamics of advanced polymeric materials, chemistry of transuranium elements and compounds, chemical and structural principles in solvent extraction, surface science related to heterogeneous catalysis, photolytic transformations of hazardous organics, DNA sequencing and mapping, and special topics.

Does Everyone's Motivational Beliefs about Physical Science Decline in Secondary School?: Heterogeneity of Adolescents' Achievement Motivation Trajectories in Physics and Chemistry.

Science.gov (United States)

Wang, Ming-Te; Chow, Angela; Degol, Jessica Lauren; Eccles, Jacquelynne Sue

2017-08-01

Students' motivational beliefs about learning physical science are critical for achieving positive educational outcomes. In this study, we incorporated expectancy-value theory to capture the heterogeneity of adolescents' motivational trajectories in physics and chemistry from seventh to twelfth grade and linked these trajectories to science-related outcomes. We used a cross-sequential design based on three different cohorts of adolescents (N = 699; 51.5 % female; 95 % European American; M ages for youngest, middle, and oldest cohorts at the first wave = 13.2, 14.1, and 15.3 years) coming from ten public secondary schools. Although many studies claim that physical science motivation declines on average over time, we identified seven differential motivational trajectories of ability self-concept and task values, and found associations of these trajectories with science achievement, advanced science course taking, and science career aspirations. Adolescents' ability self-concept and task values in physics and chemistry were also positively related and interlinked over time. Examining how students' motivational beliefs about physical science develop in secondary school offers insight into the capacity of different groups of students to successfully adapt to their changing educational environments.

Heterogeneous membranes filled with hypercrosslinked microparticle adsorbent

Czech Academy of Sciences Publication Activity Database

Hradil, Jiří; Krystl, V.; Hrabánek, P.; Bernauer, B.; Kočiřík, Milan

2005-01-01

Roč. 65, 1-2 (2005), s. 57-68 ISSN 1381-5148 R&D Projects: GA ČR GA104/03/0680 Institutional research plan: CEZ:AV0Z40500505 Keywords : heterogeneous membranes * hypercrosslinked adsorbent * microparticle s Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.565, year: 2005

Medicinal electrochemistry: integration of electrochemistry, medicinal chemistry and computational chemistry.

Science.gov (United States)

Almeida, M O; Maltarollo, V G; de Toledo, R A; Shim, H; Santos, M C; Honorio, K M

2014-01-01

Over the last centuries, there were many important discoveries in medicine that were crucial for gaining a better understanding of several physiological processes. Molecular modelling techniques are powerful tools that have been successfully used to analyse and interface medicinal chemistry studies with electrochemical experimental results. This special combination can help to comprehend medicinal chemistry problems, such as predicting biological activity and understanding drug action mechanisms. Electrochemistry has provided better comprehension of biological reactions and, as a result of many technological improvements, the combination of electrochemical techniques and biosensors has become an appealing choice for pharmaceutical and biomedical analyses. Therefore, this review will briefly outline the present scope and future advances related to the integration of electrochemical and medicinal chemistry approaches based on various applications from recent studies.

The Migration and Entrapment of DNAPLs in Physically and Chemically Heterogeneous Porous Media - Final Report - 09/15/1996 - 09/15/2000; FINAL

International Nuclear Information System (INIS)

Abriola, L. M.; Demond, A. H.

2000-01-01

experimentally validate this model. The validated numerical simulator will subsequently be employed to investigate various innovative remediation schemes such as the use of surfactants and in situ wettability alteration. The accomplishment of the research herein will: (i) lead to a better understanding of the way aqueous phase chemistry changes medium wettability; (ii) validate and/or lead to the development of methods to predict and model wettability on hydraulic property relations; (iii) lead to the development of a multiphase flow simulator that accounts for fractional wettability and concentration dependent interfacial properties; (iv) lead to an improved knowledge of the effects of pore-scale variability on scale-up issues in multiphase systems; (v) provide an understanding of the interaction of chemical and physical heterogeneity on DNAPL flow and entrapment; (vi) provide two-dimensional laboratory data sets to validate multiphase flow models for physically and chemically heterogeneous systems; and (vii) facilitate the development and implementation of innovative remediation strategies

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols.

Science.gov (United States)

Finlayson-Pitts, Barbara J

2009-09-28

While particles have significant deleterious impacts on human health, visibility and climate, quantitative understanding of their formation, composition and fates remains problematic. Indeed, in many cases, even qualitative understanding is lacking. One area of particular uncertainty is the nature of particle surfaces and how this determines interactions with gases in the atmosphere, including water, which is important for cloud formation and properties. The focus in this Perspective article is on some chemistry relevant to airborne particles and especially to reactions occurring on their surfaces. The intent is not to provide a comprehensive review, but rather to highlight a few selected examples of interface chemistry involving inorganic and organic species that may be important in the lower atmosphere. This includes sea salt chemistry, nitrate and nitrite ion photochemistry, organics on surfaces and heterogeneous reactions of oxides of nitrogen on proxies for airborne mineral dust and boundary layer surfaces. Emphasis is on the molecular level understanding that can only be gained by fully integrating experiment and theory to elucidate these complex systems.

Organic Chemistry in Action! Developing an Intervention Program for Introductory Organic Chemistry to Improve Learners' Understanding, Interest, and Attitudes

Science.gov (United States)

O'Dwyer, Anne; Childs, Peter

2014-01-01

The main areas of difficulty experienced by those teaching and learning organic chemistry at high school and introductory university level in Ireland have been identified, and the findings support previous studies in Ireland and globally. Using these findings and insights from chemistry education research (CER), the Organic Chemistry in Action!…

A Chemistry Concept Reasoning Test

Science.gov (United States)

Cloonan, Carrie A.; Hutchinson, John S.

2011-01-01

A Chemistry Concept Reasoning Test was created and validated providing an easy-to-use tool for measuring conceptual understanding and critical scientific thinking of general chemistry models and theories. The test is designed to measure concept understanding comparable to that found in free-response questions requiring explanations over…

Using Self-Efficacy Beliefs to Understand How Students in a General Chemistry Course Approach the Exam Process

Science.gov (United States)

Willson-Conrad, Angela; Kowalske, Megan Grunert

2018-01-01

Retention of students who major in STEM continues to be a major concern for universities. Many students cite poor teaching and disappointing grades as reasons for dropping out of STEM courses. Current college chemistry courses often assess what a student has learned through summative exams. To understand students' experiences of the exam process,…

DOE fundamentals handbook: Chemistry

International Nuclear Information System (INIS)

1993-01-01

The Chemistry Handbook was developed to assist nuclear facility operating contractors in providing operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of chemistry. The handbook includes information on the atomic structure of matter; chemical bonding; chemical equations; chemical interactions involved with corrosion processes; water chemistry control, including the principles of water treatment; the hazards of chemicals and gases, and basic gaseous diffusion processes. This information will provide personnel with a foundation for understanding the chemical properties of materials and the way these properties can impose limitations on the operation of equipment and systems

Silica sulfuric acid: a versatile and reusable heterogeneous catalyst ...

African Journals Online (AJOL)

... and reusable heterogeneous catalyst for the synthesis of N-acyl carbamates and ... All the reactions were done at room temperature and the N-acyl carbamates ... This method is attractive and is in a close agreement with green chemistry.

Quantum chemistry

CERN Document Server

Lowe, John P

1993-01-01

Praised for its appealing writing style and clear pedagogy, Lowe's Quantum Chemistry is now available in its Second Edition as a text for senior undergraduate- and graduate-level chemistry students. The book assumes little mathematical or physical sophistication and emphasizes an understanding of the techniques and results of quantum chemistry, thus enabling students to comprehend much of the current chemical literature in which quantum chemical methods or concepts are used as tools. The book begins with a six-chapter introduction of standard one-dimensional systems, the hydrogen atom,

Atmosphere physics and chemistry

International Nuclear Information System (INIS)

Delmas, R.; Megie, G.; Peuch, V.H.

2005-10-01

Since the 1970's, the awareness about the atmospheric pollution threat has led to a spectacular development of the researches on the complex interactions between the chemical composition of the atmosphere and the climate. This book makes a synthesis of the state-of-the-art in this very active domain of research. Content: introduction, atmosphere dynamics and transport, matter-radiation interaction and radiant transfer, physico-chemical processes, atmospheric aerosol and heterogenous chemistry, anthropic and natural emissions and deposition, stratospheric chemical system, tropospheric chemical system, polluted boundary layer, paleo-environments and ice archives, role of atmospheric chemistry in global changes, measurement principles and instruments, numerical modeling, experimental strategy, regulation and management of the atmospheric environment, index. (J.S.)

Aqueous Solution Chemistry of Plutonium

Energy Technology Data Exchange (ETDEWEB)

Clark, David L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-01-28

Things I have learned working with plutonium: Chemistry of plutonium is complex; Redox equilibria make Pu solution chemistry particularly challenging in the absence of complexing ligands; Understanding this behavior is key to successful Pu chemistry experiments; There is no suitable chemical analog for plutonium.

Nuclear chemistry

International Nuclear Information System (INIS)

Vertes, A.; Kiss, I.

1987-01-01

This book is an introduction to the application of nuclear science in modern chemistry. The first group of chapters discuss the basic phenomena and concepts of nuclear physics with emphasis on their relation to chemical problems, including the main properties and the composition of atomic nuclei, nuclear reactions, radioactive decay and interactions of radiation with matter. These chapters provide the basis for understanding the following chapters which encompass the wide scope of nuclear chemistry. The methods of the investigation of chemical structure based on the interaction of nuclear radiation with matter including positronium chemistry and other exotic atoms is elaborated in particular detail. Separate chapters are devoted to the use of radioactive tracers, the chemical consequences of nuclear processes (i.e. hot atom chemistry), radiation chemistry, isotope effects and their applications, and the operation of nuclear reactors

Nuclear chemistry

International Nuclear Information System (INIS)

Vertes, A.; Kiss, I.

1987-01-01

This book is an introduction to the application of nuclear science in modern chemistry. The first group of chapters discuss the basic phenomena and concepts of nuclear physics with emphasis on their relation to chemical problems, including the main properties and the composition of atomic nuclei, nuclear reactions, radioactive decay and interactions of radiation with matter. These chapters provide the basis for understanding the following chapters which encompass the wide scope of nuclear chemistry. The methods of the investigation of chemical structure based on the interaction of nuclear radiation with matter including positronium chemistry and other exotic atoms is elaborated in particular detail. Separate chapters are devoted to the use of radioactive tracers, the chemical consequences of nuclear processes (i.e. hot atom chemistry), radiation chemistry, isotope effects and their applications, and the operation of nuclear reactors. (Auth.)

Fundamentals of nuclear chemistry

International Nuclear Information System (INIS)

Majer, V.

1982-01-01

The author of the book has had 25 years of experience at the Nuclear Chemistry of Prague Technical University. In consequence, the book is intended as a basic textbook for students of this field. Its main objectives are an easily understandable presentation of the complex subject and in spite of the uncertainty which still characterizes the definition and subjects of nuclear chemistry - a systematic classification and logical structure. Contents: 1. Introduction (history and definition); 2. General nuclear chemistry (physical fundamentals, hot atom chemistry, interaction of nuclear radiation with matter, radioactive elements, isotope effects, isotope exchange, chemistry of radioactive trace elements); 3. Methods of nuclear chemistry of nuclear chemistry (radiochemical methods, activation, separation and enrichment chemistry); 4. Preparative nuclear chemistry (isotope production, labelled compounds); 5. Analytival nuclear chemistry; 6. Applied nuclear chemistry (isotope applications in general physical and analytical chemistry). The book is supplemented by an annex with tables, a name catalogue and a subject index which will facilitate access to important information. (RB) [de

CO chemistry/research trends in CO chemistry in the US

Energy Technology Data Exchange (ETDEWEB)

Cantacuzene, M

1978-10-01

Research trends in CO chemistry in the U.S. include the development of stable and selective homogeneous catalysts which would facilitate the removal of the heat of reaction and be resistant to sulfur poisoning for the methanation reaction, methanol synthesis, and Fischer-Tropsch synthesis; development of low-temperature homogeneous water gas shift catalysts; and research on the coordination chemistry and photochemical conversions of CO/sub 2/. In 1977, the National Science Foundation awarded 16 contracts for a total of $720,000 to promote the research in this field, including studies on chemisorption and heterogeneous catalysis (four contracts) and on transition metal complexes (ten contracts, of which seven are dedicated to metal clusters). Carbon monoxide-based processes, including water gas shift reactions, CO reduction to alkanes and alcohols, hydroformylation, and homogeneous carbonylation processes, recently developed in the U.S. are listed.

Modern trends in contemporary chemistry

International Nuclear Information System (INIS)

Javed, H.; Pervez, H.; Qadeer, R.

1993-01-01

This publication contains a collection of papers presented at symposium on M odern Trends in Contemporary Chemistry , that was held in Islamabad, Pakistan, March 6-8, 1990. The symposium was divided into five sections for presentation of about 55 scientific and technical papers and 6 review papers. The contents of these papers were of good quality in the widespread concern in new trends of chemistry. The six reviews papers covered fields of ortho metallation reactions, evaluation of heterogeneous electron transfer rate contents, macro reticular ion-exchange resins, spectrochemical analytical techniques, liquid crystal-high technology materials for practical applications and trends in advanced ceramics. (A.B.)

Chemistry and physics of fogwater collection. Final report

Energy Technology Data Exchange (ETDEWEB)

Jaeschke, W.; Enderle, K.H. (eds.)

1988-01-01

Increasing interest in the problems of air pollution and source receptor relationships has led to a significant expansion of knowledge in the field of atmospheric chemistry. In recent years the multiphase atmospheric chemistry was given great scholarly attention, and slogans like acid precipitation, dirty cloud or killer fog indicated these phenomena. The report describes results of collection and chemical analysis of fog water with emphasis or fog microphysics, of the heterogeneous atmospheric chemistry project in the Po-valley, of the development of the Great Dun Fell project, of the mountain cloud chemistry project in eastern U.S., of the design of fog water collectors and of the numerical study of the radiation fog event on October 10/11, 1982 in Albany, N.Y.

Effective Chemistry Communication in Informal Environments

Science.gov (United States)

National Academies Press, 2016

2016-01-01

Chemistry plays a critical role in daily life, impacting areas such as medicine and health, consumer products, energy production, the ecosystem, and many other areas. Communicating about chemistry in informal environments has the potential to raise public interest and understanding of chemistry around the world. However, the chemistry community…

AECL research programs in chemistry

International Nuclear Information System (INIS)

Crocker, I.H.; Eastwood, T.A.; Smith, D.R.; Stewart, R.B.; Tomlinson, M.; Torgerson, D.F.

1980-09-01

Fundamental or underlying research in chemistry is being done in AECL laboratories to further the understanding of processes involved in current nuclear energy systems and maintain an awareness of progress at the frontiers of chemical research so that new advances can be turned to advantage in future AECL endeavours. The report introduces the current research topics and describes them briefly under the following headings: radiation chemistry, isotope separation, high temperature solution chemistry, fuel reprocessing chemistry, and analytical chemistry. (auth)

DOE fundamentals handbook: Chemistry

International Nuclear Information System (INIS)

1993-01-01

This handbook was developed to assist nuclear facility operating contractors in providing operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of chemistry. This volume contains the following modules: reactor water chemistry (effects of radiation on water chemistry, chemistry parameters), principles of water treatment (purpose; treatment processes [ion exchange]; dissolved gases, suspended solids, and pH control; water purity), and hazards of chemicals and gases (corrosives [acids, alkalies], toxic compounds, compressed gases, flammable/combustible liquids)

Understanding and exploiting nanoscale surface heterogeneity for particle and cell manipulation

Science.gov (United States)

Kalasin, Surachate

This thesis explores the impact of surface heterogeneities on colloidal interactions and translates concepts to biointerfacial systems, for instance, microfluidic and biomedical devices. The thesis advances a model system, originally put forth by Kozlova: Tunable electrostatic surface heterogeneity is produced by adsorbing small amounts of cationic polyelectrolyte on a silica flat. The resulting positive electrostatic patches possess a density that is tuned from a saturated carpet down to average spacings on the order of a few hundred nanometers. At these length-scales, multiple adhesive elements (from tens to thousands) are present in the area of contact between a particle and a surface, a distinguishing feature of the thesis. Much of the literature addressing surface "heterogeneity" engineers surfaces with micron-scale features, almost always larger than the contact area between a particle and a second surface. With a nanoscale heterogeneity model, this thesis reports and quantitatively explains particle interaction behavior not typical of homogeneous interfaces. This includes (1) an adhesion threshold, a minimum average surface density of cationic patches needed for particle capture, (previously observed by Kozlova); (2) a crossover, from salt-destabilized to salt-stabilized interactions between heterogeneous surfaces with net-negative charge; (3) a shift of the adhesion threshold with shear, reducing adhesion; (4) a crossover from shear-enhanced to shear-hindered particle adhesion; (5) a range of surface compositions and processing parameters that sustain particle rolling; and (6) conditions where particles arrest immediately on contact. Through variations in ionic strength and particle size, the particle-surface contact area is systematically varied relative to the heterogeneity lengthscale. This provides a semi-quantitative explanation for the shifting of the adhesion threshold, in terms of the statistical probability of a particle being able to find a

HOW AGRICULTURAL CHEMISTRY CAN CONTRIBUTE TO DEALING WITH PROBLEMS OF ENVIRONMENTAL POLLUTION

Directory of Open Access Journals (Sweden)

Carlo Emanuele Gessa

2010-08-01

Full Text Available Soil is a complex heterogeneous system whose physical, chemical and biological properties regulate interactions with the chemical species which reach its surface. Soil chemistry is an essential tool for understanding and predicting these interactions. Soil is able to immobilize and transform organic and inorganic molecules by different mechanisms, such as complexing and redox reactions. This behaviour gives soil detoxifying capacities towards pollutants which accumulate in the environment. Pollution by heavy metals is regulated by their solubility in soil solution which in turn depends on soil pH and redox properties and metal speciation. Organic and inorganic colloidal soil fractions can promote the immobilisation, degradation, and diffusion of organic molecules such as agrochemicals, solvents, hydrocarbons and other chemicals which reach the soil by anthropic activities. Predicting the fate of xenobiotics in soil, water, air, and plant ecosystems, the recycling of biomass and the decontamination of polluted soils are of major concern to soil chemistry.

Students' Understanding of Alkyl Halide Reactions in Undergraduate Organic Chemistry

Science.gov (United States)

Cruz-Ramírez de Arellano, Daniel; Towns, Marcy H.

2014-01-01

Organic chemistry is an essential subject for many undergraduate students completing degrees in science, engineering, and pre-professional programs. However, students often struggle with the concepts and skills required to successfully solve organic chemistry exercises. Since alkyl halides are traditionally the first functional group that is…

A detailed approach to model transport, heterogeneous chemistry, and electrochemistry in solid-oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Janardhanan, V.

2007-07-01

This dissertation layes out detailed descriptions for heterogeneous chemistry, electrochemistry, and porous media transport models to simulate solid oxide fuel cells (SOFCs). An elementary like heterogeneous reaction mechanism for the steam reforming of CH4 developed in our research group is used throughout this work. Based on assumption of hydrogen oxidation as the only electrochemical reaction and single step electron transfer reaction as rate limiting, a modified Butler-Volmer equation is used to model the electrochemistry. The pertinence of various porous media transport models such as Modified Fick Model (MFM), Dusty Gas Model (DGM), Mean Transport Pore Model, Modified Maxwell Stefan Model, and Generalized Maxwell Stefan Model under reaction conditions are studied. In general MFM and DGM predictions are in good agreement with experimental data. Physically realistic electrochemical model parameters are very important for fuel cell modeling. Button cell simulations are carried out to deduce the electrochemical model parameters, and those parameters are further used in the modeling of planar cells. Button cell simulations are carried out using the commercial CFD code FLUENT coupled with DETCHEM. For all temperature ranges the model works well in predicting the experimental observations in the high current density region. However, the model predicts much higher open circuit potentials than that observed in the experiments, mainly due to the absence of coking model in the elementary heterogeneous mechanism leading to nonequilibrium compositions. Furthermore, the study presented here employs Nernst equation for the calculation of reversible potential which is strictly valid only for electrochemical equilibrium. It is assumed that the electrochemical charge transfer reaction involving H2 is fast enough to be in equilibrium. However, the comparison of model prediction with thermodynamic equilibrium reveals that this assumption is violated under very low current

Continuous Heterogeneous Photocatalysis in Serial Micro-Batch Reactors.

Science.gov (United States)

Pieber, Bartholomäus; Shalom, Menny; Antonietti, Markus; Seeberger, Peter H; Gilmore, Kerry

2018-01-29

Solid reagents, leaching catalysts, and heterogeneous photocatalysts are commonly employed in batch processes but are ill-suited for continuous-flow chemistry. Heterogeneous catalysts for thermal reactions are typically used in packed-bed reactors, which cannot be penetrated by light and thus are not suitable for photocatalytic reactions involving solids. We demonstrate that serial micro-batch reactors (SMBRs) allow for the continuous utilization of solid materials together with liquids and gases in flow. This technology was utilized to develop selective and efficient fluorination reactions using a modified graphitic carbon nitride heterogeneous catalyst instead of costly homogeneous metal polypyridyl complexes. The merger of this inexpensive, recyclable catalyst and the SMBR approach enables sustainable and scalable photocatalysis. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heterogeneous Roles and Heterogeneous Practices: Understanding the Adoption and Uses of Nonprofit Performance Evaluations

Science.gov (United States)

Eckerd, Adam; Moulton, Stephanie

2011-01-01

Evaluating the performance of nonprofit organizations has been of growing importance for the last several decades. Although there is much good that can come out of self-improvement, there is substantial heterogeneity within the sector that calls into question the usefulness of "across the board" evaluation tools. In this article, the authors…

Technetium Chemistry in HLW

International Nuclear Information System (INIS)

Hess, Nancy J.; Felmy, Andrew R.; Rosso, Kevin M.; Xia Yuanxian

2005-01-01

Tc contamination is found within the DOE complex at those sites whose mission involved extraction of plutonium from irradiated uranium fuel or isotopic enrichment of uranium. At the Hanford Site, chemical separations and extraction processes generated large amounts of high level and transuranic wastes that are currently stored in underground tanks. The waste from these extraction processes is currently stored in underground High Level Waste (HLW) tanks. However, the chemistry of the HLW in any given tank is greatly complicated by repeated efforts to reduce volume and recover isotopes. These processes ultimately resulted in mixing of waste streams from different processes. As a result, the chemistry and the fate of Tc in HLW tanks are not well understood. This lack of understanding has been made evident in the failed efforts to leach Tc from sludge and to remove Tc from supernatants prior to immobilization. Although recent interest in Tc chemistry has shifted from pretreatment chemistry to waste residuals, both needs are served by a fundamental understanding of Tc chemistry

Understanding and Using the New Guided-Inquiry AP Chemistry Laboratory Manual

Science.gov (United States)

Cacciatore, Kristen L.

2014-01-01

To support teaching and learning in the advanced placement (AP) chemistry laboratory, the College Board published a laboratory manual, "AP Chemistry Guided-Inquiry Experiments: Applying the Science Practices," in 2013 as part of the redesigned course. This article provides a discussion of the rationale for the existence of the manual as…

Effect of Electromagnetic Fields on Transfer Processes in Heterogeneous Systems

Czech Academy of Sciences Publication Activity Database

Levdansky, V.V.; Kim, H. Y.; Kim, H. C.; Smolík, Jiří; Moravec, Pavel

2001-01-01

Roč. 44, č. 5 (2001), s. 1065-1071 ISSN 0017-9310 Institutional research plan: CEZ:AV0Z4072921 Keywords : electromagnetic field * transfer processes * heterogeneous system Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.240, year: 2001

Physical chemistry and the environment

International Nuclear Information System (INIS)

Dunning, T.H. Jr.; Garrett, B.C.; Kolb, C.E. Jr.; Shaw, R.W.; Choppin, G.R.; Wagner, A.F.

1994-08-01

From the ozone hole and the greenhouse effect to plastics recycling and hazardous waste disposal, society faces a number of issues, the solutions to which require an unprecedented understanding of the properties of molecules. We are coming to realize that the environment is a coupled set of chemical systems, its dynamics determining the welfare of the biosphere and of humans in particular. These chemical systems are governed by fundamental molecular interactions, and they present chemists with an unparalleled challenge. The application of current concepts of molecular behavior and of up-to-date experimental and computational techniques can provide us with insights into the environment that are needed to mitigate past damage, to anticipate the impact of current human activity, and to avoid future insults to the environment. Environmental chemistry encompasses a number of separate, yet interlocking, areas of research. In all of these areas progress is limited by an inadequate understanding of the underlying chemical processes involved. Participation of all chemical approaches -- experimental, theoretical and computational -- and of all disciplines of chemistry -- organic, inorganic, physical, analytical and biochemistry -- will be required to provide the necessary fundamental understanding. The Symposium on ''Physical Chemistry and the Environment'' was designed to bring the many exciting and challenging physical chemistry problems involved in environmental chemistry to the attention of a larger segment of the physical chemistry community

Creating a Context for Chemistry

Science.gov (United States)

Truman Schwartz, A.

Until relatively recently, the teaching of chemistry at the college and university level in the United States has been quite traditional and oriented primarily toward the preparation of chemists. Students not concentrating in the sciences have often been poorly served by existing courses. Chemistry in Context: Applying Chemistry to Society, a textbook for nonscience majors developed under the sponsorship of the American Chemical Society, is an effort to address the needs and interests of this audience. The book introduces the phenomena and principles of chemistry within the context of socially significant issues such as global warming, ozone depletion, alternate energy sources, nutrition, and genetic engineering. The chemistry is presented as needed to inform an understanding of the central topics, and the text features student-centered activities designed to promote critical thinking and risk-benefit analysis as well as an understanding of chemical principles. This paper summarizes the origin, development, content, pedagogy, evaluation, and influence of Chemistry in Context and considers its potential implications for other disciplines and the instruction of science majors.

Sustainable Materials Management (SMM) Web Academy Webinar: Compost from Food Waste: Understanding Soil Chemistry and Soil Biology on a College/University Campus

Science.gov (United States)

This page contains information about the Sustainable Materials Management (SMM) Web Academy Webinar Series titled Compost from Food Waste:Understanding Soil Chemistry and Soil Biology on a College/University Campus

All-union conference on theoretical and applied radiation chemistry

Energy Technology Data Exchange (ETDEWEB)

Putilov, A.V.; Barashkov, N.N.

1985-01-01

The All-Union Conference on Theoretical and Applied Radiation Chemistry was held in Obninsk in October 1984. The subjects covered by the all-union conference included practically all urgent problems of modern radiation chemistry: theoretical principles of radiation chemistry, solid state radiation chemistry, radiation chemistry of heterogeneous processes, radiolysis of organic and inorganic substances, radiation polymerization and hardening, radiation chemistry of polymers, the technology of radiation chemistry and instrument making. Twenty-three plenary reports given by scientists representing the corresponding directions were devoted to an examination of the basic problems of modern radiation chemistry. Around 100 oral communications were heard and discussed at meetings of six sections operating within the framework of the conference. In addition the conference participants were able to acquaint themselves with and discuss more than 230 displays in parallel with the oral reports. Abstracts of all of the section oral reports and displays were published by the organizing committee in the form of a separate collection. The texts of the plenary reports were published in the journal Khimiya Vysokikh Energiy in 1985.

Model development of dust emission and heterogeneous chemistry within the Community Multiscale Air Quality modeling system and its application over East Asia

Directory of Open Access Journals (Sweden)

X. Dong

2016-07-01

Full Text Available The Community Multiscale Air Quality (CMAQ model has been further developed in terms of simulating natural wind-blown dust in this study, with a series of modifications aimed at improving the model's capability to predict the emission, transport, and chemical reactions of dust. The default parameterization of initial threshold friction velocity constants are revised to correct the double counting of the impact of soil moisture in CMAQ by the reanalysis of field experiment data; source-dependent speciation profiles for dust emission are derived based on local measurements for the Gobi and Taklamakan deserts in East Asia; and dust heterogeneous chemistry is also implemented. The improved dust module in the CMAQ is applied over East Asia for March and April from 2006 to 2010. The model evaluation result shows that the simulation bias of PM10 and aerosol optical depth (AOD is reduced, respectively, from −55.42 and −31.97 % by the original CMAQ to −16.05 and −22.1 % by the revised CMAQ. Comparison with observations at the nearby Gobi stations of Duolun and Yulin indicates that applying a source-dependent profile helps reduce simulation bias for trace metals. Implementing heterogeneous chemistry also results in better agreement with observations for sulfur dioxide (SO2, sulfate (SO42−, nitric acid (HNO3, nitrous oxides (NOx, and nitrate (NO3−. The investigation of a severe dust storm episode from 19 to 21 March 2010 suggests that the revised CMAQ is capable of capturing the spatial distribution and temporal variation of dust. The model evaluation also indicates potential uncertainty within the excessive soil moisture used by meteorological simulation. The mass contribution of fine-mode particles in dust emission may be underestimated by 50 %. The revised CMAQ model provides a useful tool for future studies to investigate the emission, transport, and impact of wind-blown dust over East Asia and elsewhere.

Coal-related research, organic chemistry, and catalysis

International Nuclear Information System (INIS)

Anon.

1980-01-01

Coal chemistry research topics included: H exchange at 400 0 C, breaking C-C bonds in coal, molecular weight estimation using small-angle neutron scattering, 13 C NMR spectra of coals, and tunneling during H/D isotope effects. Studies of coal conversion chemistry included thermolysis of bibenzyl and 1-naphthol, heating of coals in phenol, advanced indirect liquefaction based on Koelbel slurry Fischer-Tropsch reactor, and plasma oxidation of coal minerals. Reactions of PAHs in molten SbCl 3 , a hydrocracking catalyst, were studied. Finally, heterogeneous catalysis (desulfurization etc.) was studied using Cu, Au, and Ni surfaces. 7 figures, 6 tables

Cold Plasma: simple tool for convenient utilitarian chemistry in homogeneous and heterogeneous environments

International Nuclear Information System (INIS)

Das, Tomi Nath; Dey, Ghasi Ram

2015-07-01

Cold Plasma based experimental facilities have been commissioned (XI-XII Plan periods) in Radiation and Photochemistry Division, BARC to carry out free radical and excited state-induced chemistry in single- and mixed-phase milieu. In any reaction medium, Dielectric Barrier assisted Electric Discharge generates in situ non-equilibrium plasma constituting of electrons and photons (< 10 eV each) and chemically reactive ions, excited species and free radical transients near room temperature and pressure. Choice of reactants and nature of other added ingredient(s), type of interacting surface(s) and the dielectric characteristics, the rate and amount of electric energy dissipated within etc. control various reactions’ propensities and the natures of final products, following either routine or novel, atypical chemistry. A selection of results obtained from our laboratory highlight the development and the potential use of this technology. Constant improvements in Cold Plasma reactor types, and design, fabrication and assembly of a real-time measurement system, aiming to probe mechanistic chemistry, are also underway. (author)

Major Successes of Theory-and-Experiment-Combined Studies in Surface Chemistry and Heterogeneous Catalysis.

Energy Technology Data Exchange (ETDEWEB)

Somorjai, Gabor A.; Li, Yimin

2009-11-21

Experimental discoveries followed by theoretical interpretations that pave the way of further advances by experimentalists is a developing pattern in modern surface chemistry and catalysis. The revolution of modern surface science started with the development of surface-sensitive techniques such as LEED, XPS, AES, ISS and SIMS, in which the close collaboration between experimentalists and theorists led to the quantitative determination of surface structure and composition. The experimental discovery of the chemical activity of surface defects and the trends in the reactivity of transitional metals followed by the explanations from the theoretical studies led to the molecular level understanding of active sites in catalysis. The molecular level knowledge, in turn, provided a guide for experiments to search for new generation of catalysts. These and many other examples of successes in experiment-and-theory-combined studies demonstrate the importance of the collaboration between experimentalists and theorists in the development of modern surface science.

A computer model for one-dimensional mass and energy transport in and around chemically reacting particles, including complex gas-phase chemistry, multicomponent molecular diffusion, surface evaporation, and heterogeneous reaction

Science.gov (United States)

Cho, S. Y.; Yetter, R. A.; Dryer, F. L.

1992-01-01

Various chemically reacting flow problems highlighting chemical and physical fundamentals rather than flow geometry are presently investigated by means of a comprehensive mathematical model that incorporates multicomponent molecular diffusion, complex chemistry, and heterogeneous processes, in the interest of obtaining sensitivity-related information. The sensitivity equations were decoupled from those of the model, and then integrated one time-step behind the integration of the model equations, and analytical Jacobian matrices were applied to improve the accuracy of sensitivity coefficients that are calculated together with model solutions.

Do high school chemistry examinations inhibit deeper level understanding of dynamic reversible chemical reactions?

Science.gov (United States)

Wheeldon, R.; Atkinson, R.; Dawes, A.; Levinson, R.

2012-07-01

Background and purpose : Chemistry examinations can favour the deployment of algorithmic procedures like Le Chatelier's Principle (LCP) rather than reasoning using chemical principles. This study investigated the explanatory resources which high school students use to answer equilibrium problems and whether the marks given for examination answers require students to use approaches beyond direct application of LCP. Sample : The questionnaire was administered to 162 students studying their first year of advanced chemistry (age 16/17) in three high achieving London high schools. Design and methods : The students' explanations of reversible chemical systems were inductively coded to identify the explanatory approaches used and interviews with 13 students were used to check for consistency. AS level examination questions on reversible reactions were analysed to identify the types of explanations sought and the students' performance in these examinations was compared to questionnaire answers. Results : 19% of students used a holistic explanatory approach: when the rates of forward and reverse reactions are correctly described, recognising their simultaneous and mutually dependent nature. 36% used a mirrored reactions approach when the connected nature of the forward and reverse reactions is identified, but not their mutual dependency. 42% failed to recognize the interdependence of forward and reverse reactions (reactions not connected approach). Only 4% of marks for AS examination questions on reversible chemical systems asked for responses which went beyond either direct application of LCP or recall of equilibrium knowledge. 37% of students attained an A grade in their AS national examinations. Conclusions : Examinations favour the application of LCP making it possible to obtain the highest grade with little understanding of reversible chemical systems beyond a direct application of this algorithm. Therefore students' understanding may be attenuated so that they are

Problem-based learning on quantitative analytical chemistry course

Science.gov (United States)

Fitri, Noor

2017-12-01

This research applies problem-based learning method on chemical quantitative analytical chemistry, so called as "Analytical Chemistry II" course, especially related to essential oil analysis. The learning outcomes of this course include aspects of understanding of lectures, the skills of applying course materials, and the ability to identify, formulate and solve chemical analysis problems. The role of study groups is quite important in improving students' learning ability and in completing independent tasks and group tasks. Thus, students are not only aware of the basic concepts of Analytical Chemistry II, but also able to understand and apply analytical concepts that have been studied to solve given analytical chemistry problems, and have the attitude and ability to work together to solve the problems. Based on the learning outcome, it can be concluded that the problem-based learning method in Analytical Chemistry II course has been proven to improve students' knowledge, skill, ability and attitude. Students are not only skilled at solving problems in analytical chemistry especially in essential oil analysis in accordance with local genius of Chemistry Department, Universitas Islam Indonesia, but also have skilled work with computer program and able to understand material and problem in English.

Heterogeneous Nucleation and Growth of Nanoparticles at Environmental Interfaces.

Science.gov (United States)

Jun, Young-Shin; Kim, Doyoon; Neil, Chelsea W

2016-09-20

Mineral nucleation is a phase transformation of aqueous components to solids with an accompanying creation of new surfaces. In this evolutional, yet elusive, process, nuclei often form at environmental interfaces, which provide remarkably reactive sites for heterogeneous nucleation and growth. Naturally occurring nucleation processes significantly contribute to the biogeochemical cycles of important components in the Earth's crust, such as iron and manganese oxide minerals and calcium carbonate. However, in recent decades, these cycles have been significantly altered by anthropogenic activities, which affect the aqueous chemistry and equilibrium of both surface and subsurface systems. These alterations can trigger the dissolution of existing minerals and formation of new nanoparticles (i.e., nucleation and growth) and consequently change the porosity and permeability of geomedia in subsurface environments. Newly formed nanoparticles can also actively interact with components in natural and engineered aquatic systems, including those posing a significant hazard such as arsenic. These interactions can bilaterally influence the fate and transport of both newly formed nanoparticles and aqueous components. Due to their importance in natural and engineered processes, heterogeneous nucleation at environmental interfaces has started to receive more attention. However, a lack of time-resolved in situ analyses makes the evaluation of heterogeneous nucleation challenging because the physicochemical properties of both the nuclei and surfaces significantly and dynamically change with time and aqueous chemistry. This Account reviews our in situ kinetic studies of the heterogeneous nucleation and growth behaviors of iron(III) (hydr)oxide, calcium carbonate, and manganese (hydr)oxide minerals in aqueous systems. In particular, we utilized simultaneous small-angle and grazing incidence small-angle X-ray scattering (SAXS/GISAXS) to investigate in situ and in real-time the effects of

Medicinal chemistry and the pharmacy curriculum.

Science.gov (United States)

Khan, M O Faruk; Deimling, Michael J; Philip, Ashok

2011-10-10

The origins and advancements of pharmacy, medicinal chemistry, and drug discovery are interwoven in nature. Medicinal chemistry provides pharmacy students with a thorough understanding of drug mechanisms of action, structure-activity relationships (SAR), acid-base and physicochemical properties, and absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles. A comprehensive understanding of the chemical basis of drug action equips pharmacy students with the ability to answer rationally the "why" and "how" questions related to drug action and it sets the pharmacist apart as the chemical expert among health care professionals. By imparting an exclusive knowledge base, medicinal chemistry plays a vital role in providing critical thinking and evidence-based problem-solving skills to pharmacy students, enabling them to make optimal patient-specific therapeutic decisions. This review highlights the parallel nature of the history of pharmacy and medicinal chemistry, as well as the key elements of medicinal chemistry and drug discovery that make it an indispensable component of the pharmacy curriculum.

Evaluation of Chemical Representations in Physical Chemistry Textbooks

Science.gov (United States)

Nyachwaya, James M.; Wood, Nathan B.

2014-01-01

That different levels of representation are important for complete understanding of chemistry is an accepted fact in the chemistry education community. This study sought to uncover types of representations used in given physical chemistry textbooks. Textbooks play a central role in the teaching and learning of science (chemistry), and in some…

Misconception of pre-service chemistry teachers about the concept of resonances in organic chemistry course

Science.gov (United States)

Widarti, Hayuni Retno; Retnosari, Rini; Marfu'ah, Siti

2017-08-01

A descriptive quantitative research has been done to identify the level of understanding and misconceptions of the pre-service chemistry teachers related to the concept of resonance in the organic chemistry course. The subjects of the research were 51 students of State University of Malang, majoring Chemistry Education, currently in their fourth semester, 2015-2016 academic year who have taken the course of Organic Chemistry I. The instruments used in this research is a combination of 8 numbers of multiple choice tests with open answer questions and certainty of response index (CRI). The research findings revealed that there are still misconceptions found in the organic chemistry course, especially about the concept of resonance. There were several misconceptions of the pre-service chemistry teachers, such as resonance structures are in equilibrium with each other; resonance structures are two or more Lewis structures with different in arrangement of both atom and electron; resonance structures are only structures containing charged atoms; formal charge and resonance structures are not related; and the stability of resonance structures are only determined by location of charges in atoms found in such structures. There is also a lack of understanding of curved arrows notation to show electron pair movement.

Understanding surface structure and chemistry of single crystal lanthanum aluminate

KAUST Repository

Pramana, Stevin S.

2017-03-02

The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

Dynamic combinatorial libraries : new opportunities in systems chemistry

NARCIS (Netherlands)

Hunt, Rosemary A. R.; Otto, Sijbren; Hunt, Rosemary A.R.

2011-01-01

Combinatorial chemistry is a tool for selecting molecules with special properties. Dynamic combinatorial chemistry started off aiming to be just that. However, unlike ordinary combinatorial chemistry, the interconnectedness of dynamic libraries gives them an extra dimension. An understanding of

Connections between radiation and positronium chemistry

International Nuclear Information System (INIS)

Hirade, Tetsuya

2007-01-01

Some of the important connections between radiation chemistry and positronium chemistry started from the establishment of the spur reaction model proposed by Mogensen. Now, the modified model, the blob model proposed by Stepanov and Byakov, is making it possible to have the quantitative or semi-quantitative view of the positronium formation by using the distributions of positrons and excess electrons. Some of the interesting topics will be picked up here to understand the connections between radiation chemistry and positronium chemistry

"CHEM"opera for Chemistry Education

Science.gov (United States)

Chung, Yong Hee

2013-01-01

"CHEM"opera is an opera blended with demonstrations of chemical reactions. It has been produced and performed twice by chemistry undergraduate students at Hallym University in South Korea. It aims to demonstrate interesting chemical reactions to chemistry students, children and the public and to facilitate their understanding of the role…

Contribution from philosophy of chemistry to chemistry education: In a case of ionic liquids as technochemistry

Science.gov (United States)

Mudzakir, Ahmad; Hernani, Widhiyanti, Tuszie; Sudrajat, Devi Pratiwi

2017-08-01

Traditional chemistry education is commonly handing down of concepts, principles, and theories, such as mechanical properties, the relationship between structure and properties as well as chemical structure and chemical bonding theory, to students without engaging them in the processes of chemical inquiry. This practice leads to the lack of opportunity for the students to construct an appropriate understanding of these concepts, principles, and theories. Students are also rarely facilitated in modeling the structure and function of matter themselves. This situation shows that the philosophy of chemistry has not received as much attention from chemistry educators. The main idea of this paper is to embed philosophy of chemistry through the implementation of technochemistry in chemistry education. One of the most interesting and rapidly developing areas of modern chemistry, technologies and engineering is Ionic Liquids (ILs) as an emerging knowledge on technochemistry which can be applied to chemistry education. The developments between academic researchers and industrial developments in the ILs area are conducted in parallel. In order to overcome the existing problems of scientific development in chemistry education, the science and technology of ILs can be used for reconceptualizing the teaching and learning of chemistry to embrace the epistemology in chemistry. This study promises a potential contribution by philosophy of chemistry. The main objectives of this study are to develop: (i) a perspective based on philosophy of science considerations (rational reconstruction) in order to understand ionic liquids and (ii) teaching materials that can be used to enhance pre-service teacher's view of nature of science and technology (VNOST). The method used in the study is analytical-descriptive (elementarization), i.e. the first step in the model of educational reconstruction (MER). This study concludes that the development of the concepts and their applications of ionic

Assessing College Students' Understanding of Acid Base Chemistry Concepts

Science.gov (United States)

Wan, Yanjun Jean

2014-01-01

Typically most college curricula include three acid base models: Arrhenius', Bronsted-Lowry's, and Lewis'. Although Lewis' acid base model is generally thought to be the most sophisticated among these three models, and can be further applied in reaction mechanisms, most general chemistry curricula either do not include Lewis' acid base model, or…

Technetium Chemistry in High-Level Waste

International Nuclear Information System (INIS)

Hess, Nancy J.

2006-01-01

Tc contamination is found within the DOE complex at those sites whose mission involved extraction of plutonium from irradiated uranium fuel or isotopic enrichment of uranium. At the Hanford Site, chemical separations and extraction processes generated large amounts of high level and transuranic wastes that are currently stored in underground tanks. The waste from these extraction processes is currently stored in underground High Level Waste (HLW) tanks. However, the chemistry of the HLW in any given tank is greatly complicated by repeated efforts to reduce volume and recover isotopes. These processes ultimately resulted in mixing of waste streams from different processes. As a result, the chemistry and the fate of Tc in HLW tanks are not well understood. This lack of understanding has been made evident in the failed efforts to leach Tc from sludge and to remove Tc from supernatants prior to immobilization. Although recent interest in Tc chemistry has shifted from pretreatment chemistry to waste residuals, both needs are served by a fundamental understanding of Tc chemistry

Cell signaling heterogeneity is modulated by both cell-intrinsic and -extrinsic mechanisms: An integrated approach to understanding targeted therapy.

Science.gov (United States)

Kim, Eunjung; Kim, Jae-Young; Smith, Matthew A; Haura, Eric B; Anderson, Alexander R A

2018-03-01

During the last decade, our understanding of cancer cell signaling networks has significantly improved, leading to the development of various targeted therapies that have elicited profound but, unfortunately, short-lived responses. This is, in part, due to the fact that these targeted therapies ignore context and average out heterogeneity. Here, we present a mathematical framework that addresses the impact of signaling heterogeneity on targeted therapy outcomes. We employ a simplified oncogenic rat sarcoma (RAS)-driven mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase-protein kinase B (PI3K-AKT) signaling pathway in lung cancer as an experimental model system and develop a network model of the pathway. We measure how inhibition of the pathway modulates protein phosphorylation as well as cell viability under different microenvironmental conditions. Training the model on this data using Monte Carlo simulation results in a suite of in silico cells whose relative protein activities and cell viability match experimental observation. The calibrated model predicts distributional responses to kinase inhibitors and suggests drug resistance mechanisms that can be exploited in drug combination strategies. The suggested combination strategies are validated using in vitro experimental data. The validated in silico cells are further interrogated through an unsupervised clustering analysis and then integrated into a mathematical model of tumor growth in a homogeneous and resource-limited microenvironment. We assess posttreatment heterogeneity and predict vast differences across treatments with similar efficacy, further emphasizing that heterogeneity should modulate treatment strategies. The signaling model is also integrated into a hybrid cellular automata (HCA) model of tumor growth in a spatially heterogeneous microenvironment. As a proof of concept, we simulate tumor responses to targeted therapies in a spatially segregated tissue structure containing tumor

General Chemistry Students' Goals for Chemistry Laboratory Coursework

Science.gov (United States)

DeKorver, Brittland K.; Towns, Marcy H.

2015-01-01

Little research exists on college students' learning goals in chemistry, let alone specifically pertaining to laboratory coursework. Because students' learning goals are linked to achievement and dependent on context, research on students' goals in the laboratory context may lead to better understanding about the efficacy of lab curricula. This…

The future of discovery chemistry: quo vadis? Academic to industrial--the maturation of medicinal chemistry to chemical biology.

Science.gov (United States)

Hoffmann, Torsten; Bishop, Cheryl

2010-04-01

At Roche, we set out to think about the future role of medicinal chemistry in drug discovery in a project involving both Roche internal stakeholders and external experts in drug discovery chemistry. To derive a coherent strategy, selected scientists were asked to take extreme positions and to derive two orthogonal strategic options: chemistry as the traditional mainstream science and chemistry as the central entrepreneurial science. We believe today's role of medicinal chemistry in industry has remained too narrow. To provide the innovation that industry requires, medicinal chemistry must play its part and diversify at pace with our increasing understanding of chemical biology and network pharmacology. 2010 Elsevier Ltd. All rights reserved.

Green chemistry by nano-catalysis

KAUST Repository

Polshettiwar, Vivek

2010-01-01

Nano-materials are important in many diverse areas, from basic research to various applications in electronics, biochemical sensors, catalysis and energy. They have emerged as sustainable alternatives to conventional materials, as robust high surface area heterogeneous catalysts and catalyst supports. The nano-sized particles increase the exposed surface area of the active component of the catalyst, thereby enhancing the contact between reactants and catalyst dramatically and mimicking the homogeneous catalysts. This review focuses on the use of nano-catalysis for green chemistry development including the strategy of using microwave heating with nano-catalysis in benign aqueous reaction media which offers an extraordinary synergistic effect with greater potential than these three components in isolation. To illustrate the proof-of-concept of this "green and sustainable" approach, representative examples are discussed in this article. © 2010 The Royal Society of Chemistry.

Recent contributions of flame-sampling molecular-beam mass spectrometry to a fundamental understanding of combustion chemistry

Energy Technology Data Exchange (ETDEWEB)

Hansen, Nils [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States); Cool, Terrill A. [School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 (United States); Westmoreland, Phillip R. [Department of Chemical Engineering, University of Massachusetts, Amherst, MA 01003 (United States); Kohse-Hoeinghaus, Katharina [Department of Chemistry, Bielefeld University, D-33615 Bielefeld (Germany)

2009-04-15

Flame-sampling molecular-beam mass spectrometry of premixed, laminar, low-pressure flat flames has been demonstrated to be an efficient tool to study combustion chemistry. In this technique, flame gases are sampled through a small opening in a quartz probe, and after formation of a molecular beam, all flame species are separated using mass spectrometry. The present review focuses on critical aspects of the experimental approach including probe sampling effects, different ionization processes, and mass separation procedures. The capability for isomer-resolved flame species measurements, achievable by employing tunable vacuum-ultraviolet radiation for single-photon ionization, has greatly benefited flame-sampling molecular-beam mass spectrometry. This review also offers an overview of recent combustion chemistry studies of flames fueled by hydrocarbons and oxygenates. The identity of a variety of intermediates in hydrocarbon flames, including resonantly stabilized radicals and closed-shell intermediates, is described, thus establishing a more detailed understanding of the fundamentals of molecular-weight growth processes. Finally, molecular-beam mass-spectrometric studies of reaction paths in flames of alcohols, ethers, and esters, which have been performed to support the development and validation of kinetic models for bio-derived alternative fuels, are reviewed. (author)

Petrography and Mineral Chemistry of Magmatic and Hydrothermal Biotite in Porphyry Copper-Gold Deposits: A Tool for Understanding Mineralizing Fluid Compositional Changes During Alteration Processes

OpenAIRE

Arifudin Idrus

2018-01-01

DOI: 10.17014/ijog.5.1.47-64This study aims to understand the petrography and chemistry of both magmatic and hydrothermal biotites in porphyry copper-gold deposits, and to evaluate the fluid compositional changes during alteration processes. A total of 206 biotite grains from selected rock samples taken from the Batu Hijau porphyry Cu-Au deposit was analyzed. Detailed petrography and biotite chemistry analysis were performed on thin sections and polished thin sections, respectively, represent...

How relevant is heterogeneous chemistry on Mars? Strong tests via global mapping of water and ozone (sampled via O2 dayglow)

Science.gov (United States)

Villanueva, Geronimo Luis; Mumma, Michael J.; Novak, Robert E.

2015-11-01

Ozone and water are powerful tracers of photochemical processes on Mars. Considering that water is a condensable with a multifaceted hydrological cycle and ozone is continuously being produced / destroyed on short-time scales, their maps can test the validity of current 3D photochemical and dynamical models. Comparisons of modern GCM models (e.g., Lefèvre et al. 2004) with certain datasets (e.g., Clancy et al. 2012; Bertaux et al. 2012) point to significant disagreement, which in some cases have been related to heterogeneous (gas-dust) chemistry beyond the classical gas-gas homogeneous reactions.We address these concerns by acquiring full 2D maps of water and ozone (via O2 dayglow) on Mars, employing high spectral infrared spectrometers at ground-based telescopes (CRIRES/VLT and CSHELL/NASA-IRTF). By performing a rotational analysis on the O2 lines, we derive molecular temperature maps that we use to derive the vertical level of the emission (e.g., Novak et al. 2002). Our maps sample the full observable disk of Mars on March/25/2008 (Ls=50°, northern winter) and on Jan/29/2014 (Ls=83°, northern spring). The maps reveal a strong dependence of the O2 emission and water burden on local orography, while the temperature maps are in strong disagreement with current models. Could this be the signature of heterogeneous chemistry? We will present the global maps and will discuss possible scenarios to explain the observations.This work was partially funded by grants from NASA's Planetary Astronomy Program (344-32-51-96), NASA’s Mars Fundamental Research Program (203959.02.02.20.29), NASA’s Astrobiology Program (344-53-51), and the NSF-RUI Program (AST-805540). We thank the administration and staff of the European Southern Observatory/VLT and NASA-IRTF for awarding observing time and coordinating our observations.Bertaux, J.-L., Gondet, B., Lefèvre, F., et al. 2012. J. Geophys. Res. Pl. 117. pp. 1-9.Clancy, R.T., Sandor, B.J., Wolff, M.J., et al. 2012. J. Geophys. Res

Conflicts in Chemistry: The Case of Plastics, a Role-Playing Game for High School Chemistry Students

Science.gov (United States)

Cook, Deborah H.

2014-01-01

Conflicts in Chemistry: The Case of Plastics, an innovative role-playing activity for high school students, was developed by the Chemical Heritage Foundation to promote increased public understanding of chemistry. The pilot program included three high school teachers and their students at three different schools and documented implementation and…

A coordination chemistry approach for modeling trace element adsorption

International Nuclear Information System (INIS)

Bourg, A.C.M.

1986-01-01

The traditional distribution coefficient, Kd, is highly dependent on the water chemistry and the surface properties of the geological system being studied and is therefore quite inappropriate for use in predictive models. Adsorption, one of the many processes included in Kd values, is described here using a coordination chemistry approach. The concept of adsorption of cationic trace elements by solid hydrous oxides can be applied to natural solids. The adsorption process is thus understood in terms of a classical complexation leading to the formation of surface (heterogeneous) ligands. Applications of this concept to some freshwater, estuarine and marine environments are discussed. (author)

Perfectly Reasonable in a Practical World: Understanding Chemistry Teacher Responses to a Change Proposal

Science.gov (United States)

Westbroek, Hanna; Janssen, Fred; Doyle, Walter

2017-12-01

Curriculum ideals often get compromised as a curriculum moves through its various levels of representation. Across the different science reforms, this process of slippage is clearly present. Research shows that teacher subject matter knowledge, PCK, beliefs and context factors all influence implementation. Professional development arrangements focus on fixing deficiencies in teachers' knowledge, beliefs or work context. This approach has not solved the problem of slippage, as we still do not understand what mechanisms operate when teachers make decisions about change proposals. In this study, we unpacked the decision mechanisms of three highly qualified chemistry teachers who subsequently adapted an innovative context-based chemistry unit. In spite of a state of the art professional development arrangement and the teachers being highly qualified, slippage occurred. The teachers' goal systems were used to interpret their reasoning. A goal system is a context-dependent, within-person mental construct that consists of a hierarchy of a person's goals and means in pursuit of a task. We showed that all three teachers adopted or redesigned elements of the change proposals to meet their core goals, i.e., goals that had multiple connections with other goals. This indicated that the adaptations teachers made were perfectly reasonable ways to serve their professional goals. For change to happen, we contend that one should begin with ways to connect teachers' core goals with the lesson or unit goal demands of a proposed innovation. Change emerges from the adaptions teachers make in the service of their core goals.

1842676957299765Latent class cluster analysis to understand heterogeneity in prostate cancer treatment utilities

Directory of Open Access Journals (Sweden)

Meghani Salimah

2009-01-01

Full Text Available Abstract Background Men with prostate cancer are often challenged to choose between conservative management and a range of available treatment options each carrying varying risks and benefits. The trade-offs are between an improved life-expectancy with treatment accompanied by important risks such as urinary incontinence and erectile dysfunction. Previous studies of preference elicitation for prostate cancer treatment have found considerable heterogeneity in individuals' preferences for health states given similar treatments and clinical risks. Methods Using latent class mixture model (LCA, we first sought to understand if there are unique patterns of heterogeneity or subgroups of individuals based on their prostate cancer treatment utilities (calculated time trade-off utilities for various health states and if such unique subgroups exist, what demographic and urological variables may predict membership in these subgroups. Results The sample (N = 244 included men with prostate cancer (n = 188 and men at-risk for disease (n = 56. The sample was predominantly white (77%, with mean age of 60 years (SD ± 9.5. Most (85.9% were married or living with a significant other. Using LCA, a three class solution yielded the best model evidenced by the smallest Bayesian Information Criterion (BIC, substantial reduction in BIC from a 2-class solution, and Lo-Mendell-Rubin significance of < .001. The three identified clusters were named high-traders (n = 31, low-traders (n = 116, and no-traders (n = 97. High-traders were more likely to trade survival time associated with treatment to avoid potential risks of treatment. Low-traders were less likely to trade survival time and accepted risks of treatment. The no-traders were likely to make no trade-offs in any direction favouring the status quo. There was significant difference among the clusters in the importance of sexual activity (Pearson's χ2 = 16.55, P = 0.002; Goodman and Kruskal tau = 0.039, P < 0.001. In

Towards an Organizational Economics of Heterogeneous Capabilities

DEFF Research Database (Denmark)

Foss, Nicolai Juul

The notion of “capability” has long been influential in management research as an approach to address firm-level heterogeneity and heterogeneity in competitive outcomes. I discuss how recent advances in economics may allow for a more rigorous understanding and measurement of capability that take...

Heterogeneity and Networks

OpenAIRE

Goyal, S.

2018-01-01

This chapter shows that networks can have large and differentiated effects on behavior and then argues that social and economic pressures facilitate the formation of heterogenous networks. Thus networks can play an important role in understanding the wide diversity in human behaviour and in economic outcomes.

Learning Quantum Chemistry via a Visual-Conceptual Approach: Students' Bidirectional Textual and Visual Understanding

Science.gov (United States)

Dangur, Vered; Avargil, Shirly; Peskin, Uri; Dori, Yehudit Judy

2014-01-01

Most undergraduate chemistry courses and a few high school honors courses, which focus on physical chemistry and quantum mechanics, are highly mathematically-oriented. At the Technion, Israel Institute of Technology, we developed a new module for high school students, titled "Chemistry--From 'the Hole' to 'the Whole': From the Nanoscale to…

Molecular-level Design of Heterogeneous Chiral Catalysts

Energy Technology Data Exchange (ETDEWEB)

Gellman, Andrew John [Carnegie Mellon University; Sholl, David S. [Georgia Institute of Technology; Tysoe, Wilfred T. [University of Wisconsin - Milwaukee; Zaera, Francisco [University of California at Riverside

2013-04-28

Understanding and controlling selectivity is one of the key challenges in heterogeneous catalysis. Among problems in catalytic selectivity enantioselectivity is perhaps the most the most challenging. The primary goal of the project on “Molecular-level Design of Heterogeneous Chiral Catalysts” is to understand the origins of enantioselectivity on chiral heterogeneous surfaces and catalysts. The efforts of the project team include preparation of chiral surfaces, characterization of chiral surfaces, experimental detection of enantioselectivity on such surfaces and computational modeling of the interactions of chiral probe molecules with chiral surfaces. Over the course of the project period the team of PI’s has made some of the most detailed and insightful studies of enantioselective chemistry on chiral surfaces. This includes the measurement of fundamental interactions and reaction mechanisms of chiral molecules on chiral surfaces and leads all the way to rationale design and synthesis of chiral surfaces and materials for enantioselective surface chemistry. The PI’s have designed and prepared new materials for enantioselective adsorption and catalysis. Naturally Chiral Surfaces • Completion of a systematic study of the enantiospecific desorption kinetics of R-3-methylcyclohexanone (R-3-MCHO) on 9 achiral and 7 enantiomeric pairs of chiral Cu surfaces with orientations that span the stereographic triangle. • Discovery of super-enantioselective tartaric acid (TA) and aspartic acid (Asp) decomposition as a result of a surface explosion mechanism on Cu(643)R&S. Systematic study of super-enantiospecific TA and Asp decomposition on five enantiomeric pairs of chiral Cu surfaces. • Initial observation of the enantiospecific desorption of R- and S-propylene oxide (PO) from Cu(100) imprinted with {3,1,17} facets by L-lysine adsorption. Templated Chiral Surfaces • Initial observation of the enantiospecific desorption of R- and S-PO from Pt(111) and Pd(111

Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

NARCIS (Netherlands)

Weckhuysen, B.M.; Keller, D.E.

2003-01-01

Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular

Chemistry Division progress report for the period January 1, 1977 - December 31, 1980

International Nuclear Information System (INIS)

Moorthy, P.N.; Ramshesh, V.; Yakhmi, J.V.

1981-01-01

The research and development work of the Chemistry Division of the Bhabha Atomic Research Centre, Bombay, during the period 1977-1980 is reported in the form of individual summaries under the headings: basic research including radiation chemistry, photochemistry, kinetic and electrochemical studies, ion exchange and sorption behaviour, chemistry of metal complexes (in particular, of uranium complexes), radiation damage in solids, heterogeneous catalysts, studies in magnetism, physical properties, solid state studies, theoretical studies, reactor related programmes (including reactor chemistry, lubricants and sealants, surface studies, water chemistry), applied research and development (including materials development, purification and analytical techniques, apolied radiation chemistry etc.), and instrumentation. Work of service facilities such as workshop, analytical se services, and repair and maintenance of instruments is described. Lists of training programmes, staff publications and divisional seminars, are given. At the end a sectionwise list of staff members is also given. (M.G.B.)

Identifying and quantifying heterogeneity in high content analysis: application of heterogeneity indices to drug discovery.

Directory of Open Access Journals (Sweden)

Albert H Gough

Full Text Available One of the greatest challenges in biomedical research, drug discovery and diagnostics is understanding how seemingly identical cells can respond differently to perturbagens including drugs for disease treatment. Although heterogeneity has become an accepted characteristic of a population of cells, in drug discovery it is not routinely evaluated or reported. The standard practice for cell-based, high content assays has been to assume a normal distribution and to report a well-to-well average value with a standard deviation. To address this important issue we sought to define a method that could be readily implemented to identify, quantify and characterize heterogeneity in cellular and small organism assays to guide decisions during drug discovery and experimental cell/tissue profiling. Our study revealed that heterogeneity can be effectively identified and quantified with three indices that indicate diversity, non-normality and percent outliers. The indices were evaluated using the induction and inhibition of STAT3 activation in five cell lines where the systems response including sample preparation and instrument performance were well characterized and controlled. These heterogeneity indices provide a standardized method that can easily be integrated into small and large scale screening or profiling projects to guide interpretation of the biology, as well as the development of therapeutics and diagnostics. Understanding the heterogeneity in the response to perturbagens will become a critical factor in designing strategies for the development of therapeutics including targeted polypharmacology.

Introductory quantum chemistry

International Nuclear Information System (INIS)

Chandra, A.K.

1974-01-01

This book on quantum chemistry is primarily intended for university students at the senior undergraduate level. It serves as an aid to the basic understanding of the important concepts of quantum mechanics introduced in the field of chemistry. Various chapters of the book are devoted to the following : (i) Waves and quanta, (ii) Operator concept in quantum chemistry, (iii) Wave mechanics of some simple systems, (iv) Perturbation theory, (v) Many-electron atoms and angular momenta (vi) Molecular orbital theory and its application to the electronic structure of diatomic molecules, (vii) Chemical bonding in polyatomic molecules and (viii) Chemical applications of Hellmann-Feynman theorem. At the end of each chapter, a set of problems is given and the answers to these problems are given at the end of the book. (A.K.)

Observational Insights into N2O5 Heterogeneous Chemistry: Influencing Factors and Contribution to Wintertime Air Pollution

Science.gov (United States)

McDuffie, E. E.; Fibiger, D. L.; Womack, C.; Dube, W. P.; Lopez-Hilfiker, F.; Goldberger, L.; Thornton, J. A.; Shah, V.; Jaegle, L.; Guo, H.; Weber, R. J.; Schroder, J. C.; Campuzano Jost, P.; Jimenez, J. L.; Franchin, A.; Middlebrook, A. M.; Baasandorj, M.; Brown, S. S.

2017-12-01

Chemical mechanisms that underlie wintertime air pollution, including tropospheric ozone and aerosol nitrate, are poorly characterized. Due to colder temperatures and fewer hours of solar radiation, nocturnal heterogeneous uptake of N2O5 plays a relatively larger role during wintertime in controlling the oxidation of NOx (=NO+NO2) and its influence on ozone and soluble nitrate. After uptake to aerosol, N2O5 can act as both a nocturnal NOx reservoir and sink depending on the partitioning between its nitric acid and photo labile, ClNO2 reaction products. In addition, N2O5 itself can act as a NOx reservoir if the aerosol uptake coefficient is small. As a result, the nocturnal fate of N2O5 dictates the amount of NOx in an air parcel and the subsequent formation of aerosol nitrate and following-day ozone. Models of winter air pollution therefore require accurate parameterization of the N2O5 uptake coefficient, as well as factors that control its magnitude and N2O5 product partitioning. There are currently only a small number of ambient N2O5 and ClNO2 observations during the winter season concurrent with measurements of relevant variables such as aerosol size distributions and composition. The Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign conducted 10 nighttime research flights with the NCAR C-130 over the eastern U.S. during February and March, 2015. The more recent Utah Wintertime Fine Particulate Study (UWFPS) conducted over 20 research flights with the NOAA twin otter aircraft during January-February 2017 in three mountain basins near and including Salt Lake City, Utah. The two campaigns were similarly instrumented and have provided the first aircraft observations of N2O5, ClNO2, and aerosol composition in the wintertime boundary layer in these urban-influenced regions. Analysis of heterogeneous chemistry under a wide range of real environmental conditions provides insight into the factors controlling the N2O5 uptake coefficient

Using formative feedback to identify and support first-year chemistry students with missing or misconceptions. A Practice Report

Directory of Open Access Journals (Sweden)

Gwen Lawrie

2013-08-01

Full Text Available Students entering tertiary studies possess a diverse range of prior experiences in their academic preparation for tertiary chemistry so academics need tools to enable them to respond to issues in diversity in conceptual models possessed by entering students. Concept inventories can be used to provide formative feedback to help students identify concepts that they need to address to improve construction of subsequent understanding enabling their learning.Modular, formative learning activities that can be administered inside or outside of class in first year chemistry courses have been developed. These activities address key missing and mis-conceptions possessed by incoming student. Engagement in these learning activities by students and academics will help shift the culture of diagnostic and formative assessment within the tertiary context and address issues around the secondary/tertiary transition. This diagnostic/intervention framework is currently being trialed across five Australian tertiary institutions encompassing a large heterogeneous sample of students.

Industrial applications of radiation chemistry; Perspectives industrielles de la chimie sous rayonnement

Energy Technology Data Exchange (ETDEWEB)

Puig, Jean Rene [Commissariat a l' energie atomique et aux energies alternatives - CEA, Service de chimie-physique, CEN de Saclay (France)

1959-07-01

The status of industrial applications of radiation chemistry as it stands 6 months after the second Geneva international conference is described. The main features of the interaction of ionizing radiations with matter are briefly stated and a review is made of the best studied and the more promising systems of radiation chemistry. The fields of organics, plastics, heterogeneous catalysis are emphasized. Economies of radiation production and utilization are discussed. Reprint of a paper published in Industries atomiques - no. 5-6, 1959.

Cancer heterogeneity and imaging.

Science.gov (United States)

O'Connor, James P B

2017-04-01

There is interest in identifying and quantifying tumor heterogeneity at the genomic, tissue pathology and clinical imaging scales, as this may help better understand tumor biology and may yield useful biomarkers for guiding therapy-based decision making. This review focuses on the role and value of using x-ray, CT, MRI and PET based imaging methods that identify, measure and map tumor heterogeneity. In particular we highlight the potential value of these techniques and the key challenges required to validate and qualify these biomarkers for clinical use. Copyright © 2016. Published by Elsevier Ltd.

Using Transport Diagnostics to Understand Chemistry Climate Model Ozone Simulations

Science.gov (United States)

Strahan, S. E.; Douglass, A. R.; Stolarski, R. S.; Akiyoshi, H.; Bekki, S.; Braesicke, P.; Butchart, N.; Chipperfield, M. P.; Cugnet, D.; Dhomse, S.;

Heterogeneous catalysis at nanoscale for energy applications

CERN Document Server

Tao, Franklin (Feng); Kamat, Prashant V

2015-01-01

This book presents both the fundamentals concepts and latest achievements of a field that is growing in importance since it represents a possible solution for global energy problems.  It focuses on an atomic-level understanding of heterogeneous catalysis involved in important energy conversion processes. It presents a concise picture for the entire area of heterogeneous catalysis with vision at the atomic- and nano- scales, from synthesis, ex-situ and in-situ characterization, catalytic activity and selectivity, to mechanistic understanding based on experimental exploration and theoretical si

Effects of resource chemistry on the composition and function of stream hyporheic biofilms.

Science.gov (United States)

Hall, E.K.; Besemer, K.; Kohl, L.; Preiler, C.; Reidel, K.; Schneider, T.; Wanek, W.; Battin, T.J.

2012-01-01

Fluvial ecosystems process large quantities of dissolved organic matter as it moves from the headwater streams to the sea. In particular, hyporheic sediments are centers of high biogeochemical reactivity due to their elevated residence time and high microbial biomass and activity. However, the interaction between organic matter and microbial dynamics in the hyporheic zone remains poorly understood. We evaluated how variance in resource chemistry affected the microbial community and its associated activity in experimentally grown hyporheic biofilms. To do this we fed beech leaf leachates that differed in chemical composition to a series of bioreactors filled with sediment from a sub-alpine stream. Differences in resource chemistry resulted in differences in diversity and phylogenetic origin of microbial proteins, enzyme activity, and microbial biomass stoichiometry. Specifically, increased lignin, phenolics, and manganese in a single leachate resulted in increased phenoloxidase and peroxidase activity, elevated microbial biomass carbon:nitrogen ratio, and a greater proportion of proteins of Betaproteobacteria origin. We used this model system to attempt to link microbial form (community composition and metaproteome) with function (enzyme activity) in order to better understand the mechanisms that link resource heterogeneity to ecosystem function in stream ecosystems.

Effects of resource chemistry on the composition and function of hyporheic stream biofilms

Directory of Open Access Journals (Sweden)

Edward eHall

2012-02-01

Full Text Available Stream ecosystems process large quantities of dissolved organic matter as it moves from the headwaters to the sea. Interstitial sediments in the hyporheic zone are centers of high biogeochemical reactivity due to their high levels of microbial biomass and activity. However, the interaction between organic matter and microbial dynamics of these systems remains poorly understood. We evaluated how variance in resource chemistry affected the microbial community and its associated activity in experimentally grown interstitial biofilms. Specifically, we fed beech leaf leachates that differed in chemical composition to a series of bioreactors filled with sediment from a sub-alpine stream. Differences in resource chemistry resulted in differences in diversity and phylogenetic origin of microbial proteins, enzyme activity, and microbial biomass stoichiometry. Specifically, increased lignin, phenolics and manganese in a single leachate resulted in increased phenoloxidase and peroxidase activity, elevated microbial biomass carbon:nitrogen ratio, and a greater proportion of proteins of beta-proteobacter origin. We use this model system to link microbial form, (community composition and proteome, with function, (enzyme activity, in an attempt to develop a better understanding of the mechanisms that link resource heterogeneity to ecosystem function in stream ecosystems.

Integrating Particulate Representations into AP Chemistry and Introductory Chemistry Courses

Science.gov (United States)

Prilliman, Stephen G.

2014-01-01

The College Board's recently revised curriculum for advanced placement (AP) chemistry places a strong emphasis on conceptual understanding, including representations of particle phenomena. This change in emphasis is informed by years of research showing that students could perform algorithmic calculations but not explain those calculations…

Handbook of relativistic quantum chemistry

International Nuclear Information System (INIS)

Liu, Wenjian

2017-01-01

This handbook focuses on the foundations of relativistic quantum mechanics and addresses a number of fundamental issues never covered before in a book. For instance: How can many-body theory be combined with quantum electrodynamics? How can quantum electrodynamics be interfaced with relativistic quantum chemistry? What is the most appropriate relativistic many-electron Hamiltonian? How can we achieve relativistic explicit correlation? How can we formulate relativistic properties? - just to name a few. Since relativistic quantum chemistry is an integral component of computational chemistry, this handbook also supplements the ''Handbook of Computational Chemistry''. Generally speaking, it aims to establish the 'big picture' of relativistic molecular quantum mechanics as the union of quantum electrodynamics and relativistic quantum chemistry. Accordingly, it provides an accessible introduction for readers new to the field, presents advanced methodologies for experts, and discusses possible future perspectives, helping readers understand when/how to apply/develop the methodologies.

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

Science.gov (United States)

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…

Chemical Education Research: Improving Chemistry Learning

Science.gov (United States)

Dudley Herron, J.; Nurrenbern, Susan C.

1999-10-01

Chemical education research is the systematic investigation of learning grounded in a theoretical foundation that focuses on understanding and improving learning of chemistry. This article reviews many activities, changes, and accomplishments that have taken place in this area of scholarly activity despite its relatively recent emergence as a research area. The article describes how the two predominant broad perspectives of learning, behaviorism and constructivism, have shaped and influenced chemical education research design, analysis, and interpretation during the 1900s. Selected research studies illustrate the range of research design strategies and results that have contributed to an increased understanding of learning in chemistry. The article also provides a perspective of current and continuing challenges that researchers in this area face as they strive to bridge the gap between chemistry and education - disciplines with differing theoretical bases and research paradigms.

How to measure genetic heterogeneity

International Nuclear Information System (INIS)

Yamada, Ryo

2009-01-01

Genetic information of organisms is coded as a string of four letters, A, T, G and C, a sequence in macromolecules called deoxyribonucleic acid (DNA). DNA sequence offers blueprint of organisms and its heterogeneity determines identity and variation of species. The quantitation of this genetic heterogeneity is fundamental to understand biology. We compared previously-reported three measures, covariance matrix expression of list of loci (pair-wise r 2 ), the most popular index in genetics, and its multi-dimensional form, Ψ, and entropy-based index, ε. Thereafter we proposed two methods so that we could handle the diplotypic heterogeneity and quantitate the conditions where the number of DNA sequence samples is much smaller than the number of possible variants.

Magnetic resonance imaging of chemistry.

Science.gov (United States)

Britton, Melanie M

2010-11-01

Magnetic resonance imaging (MRI) has long been recognized as one of the most important tools in medical diagnosis and research. However, MRI is also well placed to image chemical reactions and processes, determine the concentration of chemical species, and look at how chemistry couples with environmental factors, such as flow and heterogeneous media. This tutorial review will explain how magnetic resonance imaging works, reviewing its application in chemistry and its ability to directly visualise chemical processes. It will give information on what resolution and contrast are possible, and what chemical and physical parameters can be measured. It will provide examples of the use of MRI to study chemical systems, its application in chemical engineering and the identification of contrast agents for non-clinical applications. A number of studies are presented including investigation of chemical conversion and selectivity in fixed-bed reactors, temperature probes for catalyst pellets, ion mobility during tablet dissolution, solvent dynamics and ion transport in Nafion polymers and the formation of chemical waves and patterns.

Constructing Bridges between Computational Tools in Heterogeneous and Homogeneous Catalysis

KAUST Repository

Falivene, Laura; Kozlov, Sergey M.; Cavallo, Luigi

2018-01-01

Better catalysts are needed to address numerous challenges faced by humanity. In this perspective, we review concepts and tools in theoretical and computational chemistry that can help to accelerate the rational design of homogeneous and heterogeneous catalysts. In particular, we focus on the following three topics: 1) identification of key intermediates and transition states in a reaction using the energetic span model, 2) disentanglement of factors influencing the relative stability of the key species using energy decomposition analysis and the activation strain model, and 3) discovery of new catalysts using volcano relationships. To facilitate wider use of these techniques across different areas, we illustrate their potentials and pitfalls when applied to the study of homogeneous and heterogeneous catalysts.

Constructing Bridges between Computational Tools in Heterogeneous and Homogeneous Catalysis

KAUST Repository

Falivene, Laura

2018-05-08

Better catalysts are needed to address numerous challenges faced by humanity. In this perspective, we review concepts and tools in theoretical and computational chemistry that can help to accelerate the rational design of homogeneous and heterogeneous catalysts. In particular, we focus on the following three topics: 1) identification of key intermediates and transition states in a reaction using the energetic span model, 2) disentanglement of factors influencing the relative stability of the key species using energy decomposition analysis and the activation strain model, and 3) discovery of new catalysts using volcano relationships. To facilitate wider use of these techniques across different areas, we illustrate their potentials and pitfalls when applied to the study of homogeneous and heterogeneous catalysts.

Improving Conceptions in Analytical Chemistry: The Central Limit Theorem

Science.gov (United States)

Rodriguez-Lopez, Margarita; Carrasquillo, Arnaldo, Jr.

2006-01-01

This article describes the central limit theorem (CLT) and its relation to analytical chemistry. The pedagogic rational, which argues for teaching the CLT in the analytical chemistry classroom, is discussed. Some analytical chemistry concepts that could be improved through an understanding of the CLT are also described. (Contains 2 figures.)

Heterogeneity of activated carbons in adsorption of aniline from aqueous solutions

Science.gov (United States)

Podkościelny, P.; László, K.

2007-08-01

The heterogeneity of activated carbons (ACs) prepared from different precursors is investigated on the basis of adsorption isotherms of aniline from dilute aqueous solutions at various pH values. The APET carbon prepared from polyethyleneterephthalate (PET), as well as, commercial ACP carbon prepared from peat were used. Besides, to investigate the influence of carbon surface chemistry, the adsorption was studied on modified carbons based on ACP carbon. Its various oxygen surface groups were changed by both nitric acid and thermal treatments. The Dubinin-Astakhov (DA) equation and Langmuir-Freundlich (LF) one have been used to model the phenomenon of aniline adsorption from aqueous solutions on heterogeneous carbon surfaces. Adsorption-energy distribution (AED) functions have been calculated by using an algorithm based on a regularization method. Analysis of these functions for activated carbons studied provides important comparative information about their surface heterogeneity.

Implementation of basic chemistry experiment based on metacognition to increase problem-solving and build concept understanding

Science.gov (United States)

Zuhaida, A.

2018-04-01

Implementation of the experiment have the three aspects of the goal: 1) develop basic skills of experimenting; 2) develop problem-solving skills with a scientific approach; 3) improve understanding of the subject matter. On the implementation of the experiment, students have some weaknesses include: observing, identifying problems, managing information, analyzing, and evaluating. This weakness is included in the metacognition indicator.The objective of the research is to implementation of Basic Chemistry Experiment based on metacognition to increase problem-solving skills and build concept understanding for students of Science Education Department. The method of this research is a quasi- experimental method with pretest-posttest control group design. Problem-solving skills are measured through performance assessments using rubrics from problem solving reports, and results presentation. The conceptual mastery is measured through a description test. The result of the research: (1) improve the problem solving skills of the students with very high category; (2) increase the students’ concept understanding better than the conventional experiment with the result of N-gain in medium category, and (3) increase student's response positively for learning implementation. The contribution of this research is to extend the implementation of practical learning for some subjects, and to improve the students' competence in science.

Measurement-based modeling of bromine chemistry in the boundary layer: 1. Bromine chemistry at the Dead Sea

Science.gov (United States)

Tas, E.; Peleg, M.; Pedersen, D. U.; Matveev, V.; Pour Biazar, A.; Luria, M.

2006-12-01

The Dead Sea is an excellent natural laboratory for the investigation of Reactive Bromine Species (RBS) chemistry, due to the high RBS levels observed in this area, combined with anthropogenic air pollutants up to several ppb. The present study investigated the basic chemical mechanism of RBS at the Dead Sea using a numerical one-dimensional chemical model. Simulations were based on data obtained from comprehensive measurements performed at sites along the Dead Sea. The simulations showed that the high BrO levels measured frequently at the Dead Sea could only partially be attributed to the highly concentrated Br- present in the Dead Sea water. Furthermore, the RBS activity at the Dead Sea cannot solely be explained by a pure gas phase mechanism. This paper presents a chemical mechanism which can account for the observed chemical activity at the Dead Sea, with the addition of only two heterogeneous processes: the "Bromine Explosion" mechanism and the heterogeneous decomposition of BrONO2. Ozone frequently dropped below a threshold value of ~1 to 2 ppbv at the Dead Sea evaporation ponds, and in such cases, O3 became a limiting factor for the production of BrOx (BrO+Br). The entrainment of O3 fluxes into the evaporation ponds was found to be essential for the continuation of RBS activity, and to be the main reason for the jagged diurnal pattern of BrO observed in the Dead Sea area, and for the positive correlation observed between BrO and O3 at low O3 concentrations. The present study has shown that the heterogeneous decomposition of BrONO2 has a great potential to affect the RBS activity in areas influenced by anthropogenic emissions, mainly due to the positive correlation between the rate of this process and the levels of NO2. Further investigation of the influence of the decomposition of BrONO2 may be especially important in understanding the RBS activity at mid-latitudes.

Measurement-based modeling of bromine chemistry in the boundary layer: 1. Bromine chemistry at the Dead Sea

Directory of Open Access Journals (Sweden)

E. Tas

2006-01-01

Full Text Available The Dead Sea is an excellent natural laboratory for the investigation of Reactive Bromine Species (RBS chemistry, due to the high RBS levels observed in this area, combined with anthropogenic air pollutants up to several ppb. The present study investigated the basic chemical mechanism of RBS at the Dead Sea using a numerical one-dimensional chemical model. Simulations were based on data obtained from comprehensive measurements performed at sites along the Dead Sea. The simulations showed that the high BrO levels measured frequently at the Dead Sea could only partially be attributed to the highly concentrated Br− present in the Dead Sea water. Furthermore, the RBS activity at the Dead Sea cannot solely be explained by a pure gas phase mechanism. This paper presents a chemical mechanism which can account for the observed chemical activity at the Dead Sea, with the addition of only two heterogeneous processes: the "Bromine Explosion" mechanism and the heterogeneous decomposition of BrONO2. Ozone frequently dropped below a threshold value of ~1 to 2 ppbv at the Dead Sea evaporation ponds, and in such cases, O3 became a limiting factor for the production of BrOx (BrO+Br. The entrainment of O3 fluxes into the evaporation ponds was found to be essential for the continuation of RBS activity, and to be the main reason for the jagged diurnal pattern of BrO observed in the Dead Sea area, and for the positive correlation observed between BrO and O3 at low O3 concentrations. The present study has shown that the heterogeneous decomposition of BrONO2 has a great potential to affect the RBS activity in areas influenced by anthropogenic emissions, mainly due to the positive correlation between the rate of this process and the levels of NO2. Further investigation of the influence of the decomposition of BrONO2 may be especially important in understanding the RBS activity at mid-latitudes.

The coupling effect of gas-phase chemistry and surface reactions on oxygen permeation and fuel conversion in ITM reactors

KAUST Repository

Hong, Jongsup

2015-08-01

© 2015 Elsevier B.V. The effect of the coupling between heterogeneous catalytic reactions supported by an ion transport membrane (ITM) and gas-phase chemistry on fuel conversion and oxygen permeation in ITM reactors is examined. In ITM reactors, thermochemical reactions take place in the gas-phase and on the membrane surface, both of which interact with oxygen permeation. However, this coupling between gas-phase and surface chemistry has not been examined in detail. In this study, a parametric analysis using numerical simulations is conducted to investigate this coupling and its impact on fuel conversion and oxygen permeation rates. A thermochemical model that incorporates heterogeneous chemistry on the membrane surface and detailed chemical kinetics in the gas-phase is used. Results show that fuel conversion and oxygen permeation are strongly influenced by the simultaneous action of both chemistries. It is shown that the coupling somewhat suppresses the gas-phase kinetics and reduces fuel conversion, both attributed to extensive thermal energy transfer towards the membrane which conducts it to the air side and radiates to the reactor walls. The reaction pathway and products, in the form of syngas and C2 hydrocarbons, are also affected. In addition, the operating regimes of ITM reactors in which heterogeneous- or/and homogeneous-phase reactions predominantly contribute to fuel conversion and oxygen permeation are elucidated.

Continuous-Flow Processes in Heterogeneously Catalyzed Transformations of Biomass Derivatives into Fuels and Chemicals

Directory of Open Access Journals (Sweden)

Antonio A. Romero

2012-07-01

Full Text Available Continuous flow chemical processes offer several advantages as compared to batch chemistries. These are particularly relevant in the case of heterogeneously catalyzed transformations of biomass-derived platform molecules into valuable chemicals and fuels. This work is aimed to provide an overview of key continuous flow processes developed to date dealing with a series of transformations of platform chemicals including alcohols, furanics, organic acids and polyols using a wide range of heterogeneous catalysts based on supported metals, solid acids and bifunctional (metal + acidic materials.

computational chemistry capacity building in an underprivileged ...

African Journals Online (AJOL)

dell

ABSTRACT. Computational chemistry is a fast developing branch of modern chemistry, focusing on the study of molecules to enable better understanding of the properties of substances. Its applications comprise a variety of fields, from drug design to the design of compounds with desired properties. (e.g., catalysts with ...

An estimating function approach to linkage heterogeneity

Indian Academy of Sciences (India)

Testing linkage heterogeneity between two loci is an important issue in genetics. Currently, there are ... on linkage heterogeneity can help people to better understand complex .... χ2(F − 2) + cχ2 (1), where c is a constant (see Appendix). Here, it can be ..... gin, ancestry, gender, age, etc., for purpose of dividing sub- groups to ...

Nanoengineering of Ruthenium and Platinum-based Nanocatalysts by Continuous-Flow Chemistry for Renewable Energy Applications

KAUST Repository

AlYami, Noktan Mohammed

2017-01-01

This thesis presents an integrated study of nanocatalysts for heterogenous catalytic and electrochemical processes using pure ruthenium (Ru) with mixed-phase and platinum-based nanomaterials synthesized by continuous-flow chemistry. There are three

Mapping quorum sensing onto neural networks to understand collective decision making in heterogeneous microbial communities

Science.gov (United States)

Yusufaly, Tahir I.; Boedicker, James Q.

2017-08-01

Microbial communities frequently communicate via quorum sensing (QS), where cells produce, secrete, and respond to a threshold level of an autoinducer (AI) molecule, thereby modulating gene expression. However, the biology of QS remains incompletely understood in heterogeneous communities, where variant bacterial strains possess distinct QS systems that produce chemically unique AIs. AI molecules bind to ‘cognate’ receptors, but also to ‘non-cognate’ receptors found in other strains, resulting in inter-strain crosstalk. Understanding these interactions is a prerequisite for deciphering the consequences of crosstalk in real ecosystems, where multiple AIs are regularly present in the same environment. As a step towards this goal, we map crosstalk in a heterogeneous community of variant QS strains onto an artificial neural network model. This formulation allows us to systematically analyze how crosstalk regulates the community’s capacity for flexible decision making, as quantified by the Boltzmann entropy of all QS gene expression states of the system. In a mean-field limit of complete cross-inhibition between variant strains, the model is exactly solvable, allowing for an analytical formula for the number of variants that maximize capacity as a function of signal kinetics and activation parameters. An analysis of previous experimental results on the Staphylococcus aureus two-component Agr system indicates that the observed combination of variant numbers, gene expression rates and threshold concentrations lies near this critical regime of parameter space where capacity peaks. The results are suggestive of a potential evolutionary driving force for diversification in certain QS systems.

Solvent effects in chemistry

CERN Document Server

Buncel, Erwin

2015-01-01

This book introduces the concepts, theory and experimental knowledge concerning solvent effects on the rate and equilibrium of chemical reactions of all kinds.  It begins with basic thermodynamics and kinetics, building on this foundation to demonstrate how a more detailed understanding of these effects may be used to aid in determination of reaction mechanisms, and to aid in planning syntheses. Consideration is given to theoretical calculations (quantum chemistry, molecular dynamics, etc.), to statistical methods (chemometrics), and to modern day concerns such as ""green"" chemistry, where ut

The chemistry of silicon

CERN Document Server

Rochow, E G; Emeléus, H J; Nyholm, Ronald

1975-01-01

Pergamon Texts in Organic Chemistry, Volume 9: The Chemistry of Silicon presents information essential in understanding the chemical properties of silicon. The book first covers the fundamental aspects of silicon, such as its nuclear, physical, and chemical properties. The text also details the history of silicon, its occurrence and distribution, and applications. Next, the selection enumerates the compounds and complexes of silicon, along with organosilicon compounds. The text will be of great interest to chemists and chemical engineers. Other researchers working on research study involving s

"Sizing" Heterogeneous Chemistry in the Conversion of Gaseous Dimethyl Sulfide to Atmospheric Particles.

Science.gov (United States)

Enami, Shinichi; Sakamoto, Yosuke; Hara, Keiichiro; Osada, Kazuo; Hoffmann, Michael R; Colussi, Agustín J

2016-02-16

The oxidation of biogenic dimethyl sulfide (DMS) emissions is a global source of cloud condensation nuclei. The amounts of the nucleating H2SO4(g) species produced in such process, however, remain uncertain. Hydrophobic DMS is mostly oxidized in the gas phase into H2SO4(g) + DMSO(g) (dimethyl sulfoxide), whereas water-soluble DMSO is oxidized into H2SO4(g) in the gas phase and into SO4(2-) + MeSO3(-) (methanesulfonate) on water surfaces. R = MeSO3(-)/(non-sea-salt SO4(2-)) ratios would therefore gauge both the strength of DMS sources and the extent of DMSO heterogeneous oxidation if Rhet = MeSO3(-)/SO4(2-) for DMSO(aq) + ·OH(g) were known. Here, we report that Rhet = 2.7, a value obtained from online electrospray mass spectra of DMSO(aq) + ·OH(g) reaction products that quantifies the MeSO3(-) produced in DMSO heterogeneous oxidation on aqueous aerosols for the first time. On this basis, the inverse R dependence on particle radius in size-segregated aerosol collected over Syowa station and Southern oceans is shown to be consistent with the competition between DMSO gas-phase oxidation and its mass accommodation followed by oxidation on aqueous droplets. Geographical R variations are thus associated with variable contributions of the heterogeneous pathway to DMSO atmospheric oxidation, which increase with the specific surface area of local aerosols.

Advances in high temperature chemistry 1

CERN Document Server

Eyring, Leroy

2013-01-01

Advances in High Temperature Chemistry, Volume 1 describes the complexities and special and changing characteristics of high temperature chemistry. After providing a brief definition of high temperature chemistry, this nine-chapter book goes on describing the experiments and calculations of diatomic transition metal molecules, as well as the advances in applied wave mechanics that may contribute to an understanding of the bonding, structure, and spectra of the molecules of high temperature interest. The next chapter provides a summary of gaseous ternary compounds of the alkali metals used in

Handbook of relativistic quantum chemistry

Energy Technology Data Exchange (ETDEWEB)

Liu, Wenjian (ed.) [Peking Univ., Beijing (China). Center for Computational Science and Engineering

2017-03-01

This handbook focuses on the foundations of relativistic quantum mechanics and addresses a number of fundamental issues never covered before in a book. For instance: How can many-body theory be combined with quantum electrodynamics? How can quantum electrodynamics be interfaced with relativistic quantum chemistry? What is the most appropriate relativistic many-electron Hamiltonian? How can we achieve relativistic explicit correlation? How can we formulate relativistic properties? - just to name a few. Since relativistic quantum chemistry is an integral component of computational chemistry, this handbook also supplements the ''Handbook of Computational Chemistry''. Generally speaking, it aims to establish the 'big picture' of relativistic molecular quantum mechanics as the union of quantum electrodynamics and relativistic quantum chemistry. Accordingly, it provides an accessible introduction for readers new to the field, presents advanced methodologies for experts, and discusses possible future perspectives, helping readers understand when/how to apply/develop the methodologies.

The quadruple bottom line: the advantages of incorporating Green Chemistry into the undergraduate chemistry major

Science.gov (United States)

Bodner, George M.

2017-08-01

When the author first became involved with the Green Chemistry movement, he noted that his colleagues in industry who were involved in one of the ACS Green Chemistry Institute® industrial roundtables emphasized the take-home message they described as the "triple bottom line." They noted that introducing Green Chemistry in industrial settings had economic, social, and environmental benefits. As someone who first went to school at age 5, and has been "going to school" most days for 65 years, it was easy for the author to see why introducing Green Chemistry into academics had similar beneficial effects within the context of economic, social and environmental domains at the college/university level. He was prepared to understand why faculty who had taught traditional courses often saw the advantage of incorporating Green Chemistry into the courses they teach. What was not as obvious is why students who were encountering chemistry for the first time were often equally passionate about the Green Chemistry movement. Recent attention has been paid, however, to a model that brings clarity to the hitherto vague term of "relevance" that might explain why integrating Green Chemistry into the undergraduate chemistry classroom can achieve a "quadruple bottom-line" for students because of potentially positive effects of adding a domain of "relevance" to the existing economic, social, and environmental domains.

Spatial heterogeneity study of vegetation coverage at Heihe River Basin

Science.gov (United States)

Wu, Lijuan; Zhong, Bo; Guo, Liyu; Zhao, Xiangwei

2014-11-01

Spatial heterogeneity of the animal-landscape system has three major components: heterogeneity of resource distributions in the physical environment, heterogeneity of plant tissue chemistry, heterogeneity of movement modes by the animal. Furthermore, all three different types of heterogeneity interact each other and can either reinforce or offset one another, thereby affecting system stability and dynamics. In previous studies, the study areas are investigated by field sampling, which costs a large amount of manpower. In addition, uncertain in sampling affects the quality of field data, which leads to unsatisfactory results during the entire study. In this study, remote sensing data is used to guide the sampling for research on heterogeneity of vegetation coverage to avoid errors caused by randomness of field sampling. Semi-variance and fractal dimension analysis are used to analyze the spatial heterogeneity of vegetation coverage at Heihe River Basin. The spherical model with nugget is used to fit the semivariogram of vegetation coverage. Based on the experiment above, it is found, (1)there is a strong correlation between vegetation coverage and distance of vegetation populations within the range of 0-28051.3188m at Heihe River Basin, but the correlation loses suddenly when the distance greater than 28051.3188m. (2)The degree of spatial heterogeneity of vegetation coverage at Heihe River Basin is medium. (3)Spatial distribution variability of vegetation occurs mainly on small scales. (4)The degree of spatial autocorrelation is 72.29% between 25% and 75%, which means that spatial correlation of vegetation coverage at Heihe River Basin is medium high.

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

Science.gov (United States)

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…

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

Science.gov (United States)

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…

Asymmetric Translation between Multiple Representations in Chemistry

Science.gov (United States)

Lin, Yulan I.; Son, Ji Y.; Rudd, James A., II

2016-01-01

Experts are more proficient in manipulating and translating between multiple representations (MRs) of a given concept than novices. Studies have shown that instruction using MR can increase student understanding of MR, and one model for MR instruction in chemistry is the chemistry triplet proposed by Johnstone. Concreteness fading theory suggests…

Nitric oxide reduction in coal combustion: role of char surface complexes in heterogeneous reactions.

Science.gov (United States)

Arenillas, Ana; Rubiera, Fernando; Pis, José J

2002-12-15

Nitrogen oxides are one of the major environmental problems arising from fossil fuel combustion. Coal char is relatively rich in nitrogen, and so this is an important source of nitrogen oxides during coal combustion. However, due to its carbonaceous nature, char can also reduce NO through heterogeneous reduction. The objectives of this work were on one hand to compare NO emissions from coal combustion in two different types of equipment and on the other hand to study the influence of char surface chemistry on NO reduction. A series of combustion tests were carried out in two different scale devices: a thermogravimetric analyzer coupled to a mass spectrometer and an FTIR (TG-MS-FTIR) and a fluidized bed reactor with an on line battery of analyzers. The TG-MS-FTIR system was also used to perform a specific study on NO heterogeneous reduction reactions using chars with different surface chemistry. According to the results obtained, it can be said that the TG-MS-FTIR system provides valuable information about NO heterogeneous reduction and it can give good trends of the behavior in other combustion equipments (i.e., fluidized bed combustors). It has been also pointed out that NO-char interaction depends to a large extent on temperature. In the low-temperature range (800 degrees C), a different mechanism is involved in NO heterogeneous reduction, the nature of the carbon matrix being a key factor.

Intratumor and Intertumor Heterogeneity in Melanoma

Directory of Open Access Journals (Sweden)

Tomasz M. Grzywa

2017-12-01

Full Text Available Melanoma is a cancer that exhibits one of the most aggressive and heterogeneous features. The incidence rate escalates. A high number of clones harboring various mutations contribute to an exceptional level of intratumor heterogeneity of melanoma. It also refers to metastases which may originate from different subclones of primary lesion. Such component of the neoplasm biology is termed intertumor and intratumor heterogeneity. These levels of tumor heterogeneity hinder accurate diagnosis and effective treatment. The increasing number of research on the topic reflects the need for understanding limitation or failure of contemporary therapies. Majority of analyses concentrate on mutations in cancer-related genes. Novel high-throughput techniques reveal even higher degree of variations within a lesion. Consolidation of theories and researches indicates new routes for treatment options such as targets for immunotherapy. The demand for personalized approach in melanoma treatment requires extensive knowledge on intratumor and intertumor heterogeneity on the level of genome, transcriptome/proteome, and epigenome. Thus, achievements in exploration of melanoma variety are described in details. Particularly, the issue of tumor heterogeneity or homogeneity given BRAF mutations is discussed.

Surface science and heterogeneous catalysis

International Nuclear Information System (INIS)

Somorjai, G.A.

1980-05-01

The catalytic reactions studied include hydrocarbon conversion over platinum, the transition metal-catalyzed hydrogenation of carbon monoxide, and the photocatalyzed dissociation of water over oxide surfaces. The method of combined surface science and catalytic studies is similar to those used in synthetic organic chemistry. The single-crystal models for the working catalyst are compared with real catalysts by comparing the rates of cyclopropane ring opening on platinum and the hydrogenation of carbon monoxide on rhodium single crystal surface with those on practical commercial catalyst systems. Excellent agreement was obtained for these reactions. This document reviews what was learned about heterogeneous catalysis from these surface science approaches over the past 15 years and present models of the active catalyst surface

Inorganic chemistry and medicine

International Nuclear Information System (INIS)

Sadler, P.J.; Guo, Z.

1999-01-01

Inorganic chemistry is beginning to have a major impact on medicine. Not only does it offer the prospect of the discovery of truly novel drugs and diagnostic agents, but it promises to make a major contribution to our understanding of the mechanism of action of organic drugs too. Most of this article is concerned with recent developments in medicinal coordination chemistry. The role of metal organic compounds of platinum, titanium, ruthenium, gallium, bismuth, gold, gadolinium, technetium, silver, cobalt in the treatment or diagnosis of common diseases are briefly are examined

Chemistry and climate change

International Nuclear Information System (INIS)

Bernier, Jean-Claude; Brasseur, Guy; Brechet, Yves; Candel, Sebastien; Cazenave, Anny; Courtillot, Vincent; Fontecave, Marc; Garnier, Emmanuel; Goebel, Philippe; Legrand, Jack; Legrand, Michel; Le Treut, Herve; Mauberger, Pascal; Dinh-Audouin, Minh-Thu; Olivier, Daniele; Rigny, Paul; Bigot, Bernard

2016-01-01

In its first part, this collective publication addresses the decennial and centuries-old variations of climate: perspectives and implications of climate change for the 21. century, questions remaining about the understanding of climate change from its sources to its modelling, extreme climate variations and societies during the last millennium. The contributions of the second part outline how chemistry is a tool to study climate change: ice chemistry as an archive of our past environment, observations and predictions on sea level rise, relationship between atmosphere chemistry and climate. The third set of contributions discusses the transformation of the energy system for a cleaner atmosphere and the management of the climate risk: the chemical processing of CO_2, actions of chemical companies to support the struggle against climate change, relationship between barrel price and renewable energies, relationship between grid complexity and green energy. The last part outlines the role chemistry can have to be able to do without fossil fuels: chemistry in front of challenges of transformation of the energy system, the use of micro-algae, the use of hydrogen as a vector of energy transition

Tumor Heterogeneity and Drug Resistance

International Nuclear Information System (INIS)

Kucerova, L.; Skolekova, S.; Kozovska, Z.

2015-01-01

New generation of sequencing methodologies revealed unexpected complexity and genomic alterations linked with the tumor subtypes. This diversity exists across the tumor types, histologic tumor subtypes and subsets of the tumor cells within the same tumor. This phenomenon is termed tumor heterogeneity. Regardless of its origin and mechanisms of development it has a major impact in the clinical setting. Genetic, phenotypic and expression pattern diversity of tumors plays critical role in the selection of suitable treatment and also in the prognosis prediction. Intratumoral heterogeneity plays a key role in the intrinsic and acquired chemoresistance to cytotoxic and targeted therapies. In this review we focus on the mechanisms of intratumoral and inter tumoral heterogeneity and their relationship to the drug resistance. Understanding of the mechanisms and spatiotemporal dynamics of tumor heterogeneity development before and during the therapy is important for the ability to design individual treatment protocols suitable in the given molecular context. (author)

Quantum Chemistry; A concise introduction for students of physics, chemistry, biochemistry and materials science

Science.gov (United States)

Thakkar, Ajit J.

2017-09-01

This book provides non-specialists with a basic understanding of the underlying concepts of quantum chemistry. It is both a text for second- or third-year undergraduates and a reference for researchers who need a quick introduction or refresher. All chemists and many biochemists, materials scientists, engineers, and physicists routinely use spectroscopic measurements and electronic structure computations in their work. The emphasis of Quantum Chemistry on explaining ideas rather than enumerating facts or presenting procedural details makes this an excellent foundation text/reference.

Graphene-Based Nanomaterials as Heterogeneous Acid Catalysts: A Comprehensive Perspective

Directory of Open Access Journals (Sweden)

Bhaskar Garg

2014-09-01

Full Text Available Acid catalysis is quite prevalent and probably one of the most routine operations in both industrial processes and research laboratories worldwide. Recently, “graphene”, a two dimensional single-layer carbon sheet with hexagonal packed lattice structure, imitative of nanomaterials, has shown great potential as alternative and eco-friendly solid carbocatalyst for a variety of acid-catalyzed reactions. Owing to their exceptional physical, chemical, and mechanical properties, graphene-based nanomaterials (G-NMs offer highly stable Brønsted acidic sites, high mass transfer, relatively large surface areas, water tolerant character, and convenient recoverability as well as recyclability, whilst retaining high activity in acid-catalyzed chemical reactions. This comprehensive review focuses on the chemistry of G-NMs, including their synthesis, characterization, properties, functionalization, and up-to-date applications in heterogeneous acid catalysis. In line with this, in certain instances readers may find herein some criticisms that should be taken as constructive and would be of value in understanding the scope and limitations of current approaches utilizing graphene and its derivatives for the same.

Physical Chemistry Chemical Kinetics and Reaction Mechanism

CERN Document Server

Trimm, Harold H

2011-01-01

Physical chemistry covers diverse topics, from biochemistry to materials properties to the development of quantum computers. Physical chemistry applies physics and math to problems that interest chemists, biologists, and engineers. Physical chemists use theoretical constructs and mathematical computations to understand chemical properties and describe the behavior of molecular and condensed matter. Their work involves manipulations of data as well as materials. Physical chemistry entails extensive work with sophisticated instrumentation and equipment as well as state-of-the-art computers. This

Understanding heterogeneity of social preferences for fire prevention management

DEFF Research Database (Denmark)

Varela, Elsa; Jacobsen, Jette Bredahl; Soliño, Mario

2014-01-01

The forest area burnt annually in the European Mediterranean region has more than doubled since the 1970s. In these forests, the main preventive action consists of forest compartmentalization by fuel break networks, which entail high costs and sometimes significant negative impacts. While many...... studies look at public preferences for fire suppression, this study analyses the heterogeneity of social preferences for fire prevention. The visual characteristics of fire prevention structures are very familiar to respondents, but their management is unfamiliar, which raises specific attention in terms...... for the density of fuel breaks. These results are important for designing fire prevention policies that are efficient and acceptable by the population....

The chemistry-climate model ECHAM6.3-HAM2.3-MOZ1.0

Science.gov (United States)

Schultz, Martin G.; Stadtler, Scarlet; Schröder, Sabine; Taraborrelli, Domenico; Franco, Bruno; Krefting, Jonathan; Henrot, Alexandra; Ferrachat, Sylvaine; Lohmann, Ulrike; Neubauer, David; Siegenthaler-Le Drian, Colombe; Wahl, Sebastian; Kokkola, Harri; Kühn, Thomas; Rast, Sebastian; Schmidt, Hauke; Stier, Philip; Kinnison, Doug; Tyndall, Geoffrey S.; Orlando, John J.; Wespes, Catherine

2018-05-01

The chemistry-climate model ECHAM-HAMMOZ contains a detailed representation of tropospheric and stratospheric reactive chemistry and state-of-the-art parameterizations of aerosols using either a modal scheme (M7) or a bin scheme (SALSA). This article describes and evaluates the model version ECHAM6.3-HAM2.3-MOZ1.0 with a focus on the tropospheric gas-phase chemistry. A 10-year model simulation was performed to test the stability of the model and provide data for its evaluation. The comparison to observations concentrates on the year 2008 and includes total column observations of ozone and CO from IASI and OMI, Aura MLS observations of temperature, HNO3, ClO, and O3 for the evaluation of polar stratospheric processes, an ozonesonde climatology, surface ozone observations from the TOAR database, and surface CO data from the Global Atmosphere Watch network. Global budgets of ozone, OH, NOx, aerosols, clouds, and radiation are analyzed and compared to the literature. ECHAM-HAMMOZ performs well in many aspects. However, in the base simulation, lightning NOx emissions are very low, and the impact of the heterogeneous reaction of HNO3 on dust and sea salt aerosol is too strong. Sensitivity simulations with increased lightning NOx or modified heterogeneous chemistry deteriorate the comparison with observations and yield excessively large ozone budget terms and too much OH. We hypothesize that this is an impact of potential issues with tropical convection in the ECHAM model.

An overview: origins and development of green chemistry

NARCIS (Netherlands)

Linthorst, J.A.

2009-01-01

This article provides an overview of the origins and development of green chemistry. Aiming to contribute to the understanding of green chemistry, basically from a historical point of view, this overview argues that contextual influences and the user friendliness of the term are drivers for the

Life's Biological Chemistry: A Destiny or Destination Starting from Prebiotic Chemistry?

Science.gov (United States)

Krishnamurthy, Ramanarayanan

2018-06-05

Research into understanding the origins -and evolution- of life has long been dominated by the concept of taking clues from extant biology and extrapolating its molecules and pathways backwards in time. This approach has also guided the search for solutions to the problem of how contemporary biomolecules would have arisen directly from prebiotic chemistry on early earth. However, the continuing difficulties in finding universally convincing solutions in connecting prebiotic chemistry to biological chemistry should give us pause, and prompt us to rethink this concept of treating extant life's chemical processes as the sole end goal and, therefore, focusing only -and implicitly- on the respective extant chemical building blocks. Rather, it may be worthwhile "to set aside the goal" and begin with what would have been plausible prebiotic reaction mixtures (which may have no obvious or direct connection to life's chemical building blocks and processes) - and allow their chemistries and interactions, under different geochemical constraints, to guide and illuminate as to what processes and systems can emerge. Such a conceptual approach gives rise to the prospect that chemistry of life-as-we-know-it is not the only result (not a "destiny"), but one that has emerged among many potential possibilities (a "destination"). This postulate, in turn, could impact the way we think about chemical signatures and criteria used in the search for alternative and extraterrestrial "life". As a bonus, we may discover the chemistries and pathways naturally that led to the emergence of life as we know it. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mo-II Cluster Complex-Based Coordination Polymer as an Efficient Heterogeneous Catalyst in the Suzuki–Miyaura Coupling Reaction

Czech Academy of Sciences Publication Activity Database

Bůžek, Daniel; Hynek, Jan; Kučeráková, Monika; Kirakci, Kaplan; Demel, Jan; Lang, Kamil

2016-01-01

Roč. 2016, č. 28 (2016), s. 4668-4673 ISSN 1434-1948 R&D Projects: GA ČR GA13-05114S; GA ČR GA15-12653S EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:61388980 ; RVO:68378271 Keywords : C–C coupling * Heterogeneous catalysis * Molybdenum * Palladium * Polymers Subject RIV: CA - Inorganic Chemistry ; CF - Physical ; Theoretical Chemistry (FZU-D) Impact factor: 2.444, year: 2016

Underlying chemistry research for the nuclear fuel waste management program

International Nuclear Information System (INIS)

Torgerson, D.F.; Sagert, N.H.; Shoesmith, D.W.; Taylor, P.

1984-04-01

This document reviews the underlying chemistry research part of the Canadian Nuclear Fuel Waste Management Program, carried out in the Research Chemistry Branch. This research is concerned with developing the basic chemical knowledge and under-standing required in other parts of the Program. There are four areas of underlying research: Waste Form Chemistry, Solute and Solution Chemistry, Rock-Water-Waste Interactions, and Abatement and Monitoring of Gas-Phase Radionuclides

Research in nuclear chemistry: current status and future perspectives

International Nuclear Information System (INIS)

Reddy, A.V.R.

2007-01-01

Research in nuclear chemistry has seen a huge growth over the last few decades. The large umbrella of nuclear chemistry includes several research areas such as nuclear fission, reactions, spectroscopy, nuclear probes and nuclear analytical techniques. Currently, nuclear chemistry research has extended its horizon into various applications like nuclear medicine, isotopes for understanding physico chemical processes, and addressing environmental and biomedical problems. Tremendous efforts are going on for synthesizing new elements (isotopes), isolating physically or chemically wherever possible and investigating their properties. Theses studies are useful to understand nuclear and chemical properties at extreme ends of instability. In addition, nuclear chemists are making substantial contribution to astrophysics and other related areas. During this talk, a few of the contributions made by nuclear chemistry group of BARC will be discussed and possible future areas of research will be enumerated. (author)

Research for the advancement of green chemistry practice: Studies in atmospheric and educational chemistry

Science.gov (United States)

Cullipher, Steven Gene

Green chemistry is a philosophy of chemistry that emphasizes a decreasing dependence on limited non-renewable resources and an increasing focus on preventing pollution byproducts of the chemical industry. In short, it is the discipline of chemistry practiced through the lens of environmental stewardship. In an effort to advance the practice of green chemistry, three studies will be described that have ramifications for the practice. The first study examines the atmospheric oxidation of a hydrofluorinated ether, a third-generation CFC replacement compound with primarily unknown atmospheric degradation products. Determination of these products has the potential to impact decisions on refrigerant usage in the future. The second study examines chemistry students' development of understanding benefits-costs-risks analysis when presented with two real-world scenarios: refrigerant choice and fuel choice. By studying how benefits-costs-risks thinking develops, curricular materials and instructional approaches can be designed to better foster the development of an ability that is both necessary for green chemists and important in daily decision-making for non-chemists. The final study uses eye tracking technology to examine students' abilities to interpret molecular properties from structural information in the context of global warming. Such abilities are fundamental if chemists are to appropriately assess risks and hazards of chemistry practice.

Targeting population heterogeneity for optimal cell factories

DEFF Research Database (Denmark)

Heins, Anna-Lena; Carlqvist, Magnus; Helmark, S.

the heterogeneity level of the population. To further investigate these phenomena and gain a deeper understanding of population heterogeneity, Saccharomyces cerevisiae growth reporter strains based on the expression of green fluorescent protein (GFP) were constructed which enabled us to perform single cell level...... analysis, and thereby created the possibility to map population heterogeneity. A factorial design with pH, glucose concentration and oxygen level was performed in batch cultivations using the growth reporter strains to evaluate the effect of those environmental factors on heterogeneity level and amount......To achieve an efficient production process, it is essential to optimize both the strain and the cultivation conditions. Traditionally, a microbial population has been considered homogeneous in optimization studies of fermentation processes. However, research has shown that a typical microbial...

Glioblastoma Multiforme: A Look Inside Its Heterogeneous Nature

International Nuclear Information System (INIS)

Inda, Maria-del-Mar; Bonavia, Rudy; Seoane, Joan

2014-01-01

Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM), the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape

Glioblastoma Multiforme: A Look Inside Its Heterogeneous Nature

Energy Technology Data Exchange (ETDEWEB)

Inda, Maria-del-Mar, E-mail: mminda@vhio.net; Bonavia, Rudy [Translational Research Program, Vall d’Hebron Institute of Oncology (VHIO), Vall d’Hebron University Hospital, 119-129 Passeig Vall d’Hebron, Barcelona 08035 (Spain); Seoane, Joan [Translational Research Program, Vall d’Hebron Institute of Oncology (VHIO), Vall d’Hebron University Hospital, 119-129 Passeig Vall d’Hebron, Barcelona 08035 (Spain); Catalan Institution of Research and Advanced Studies (ICREA), Barcelona 08035 (Spain)

2014-01-27

Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM), the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape.

Glioblastoma Multiforme: A Look Inside Its Heterogeneous Nature

Directory of Open Access Journals (Sweden)

Maria-del-Mar Inda

2014-01-01

Full Text Available Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM, the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape.

Glioblastoma multiforme: a look inside its heterogeneous nature.

Science.gov (United States)

Inda, Maria-Del-Mar; Bonavia, Rudy; Seoane, Joan

2014-01-27

Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM), the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape.

How sonochemistry contributes to green chemistry?

Science.gov (United States)

Chatel, Gregory

2018-01-01

Based on the analyses of papers from the literature, and especially those published in Ultrasonics Sonochemistry journal, the contribution of sonochemistry to green chemistry area has been discussed here. Important reminders and insights on the good practices and considerations have been made to understand and demonstrate how sonochemistry can continue to efficiently contribute to green chemistry area in the further studies. Copyright © 2017 Elsevier B.V. All rights reserved.

Engineering Microbial Metabolite Dynamics and Heterogeneity.

Science.gov (United States)

Schmitz, Alexander C; Hartline, Christopher J; Zhang, Fuzhong

2017-10-01

As yields for biological chemical production in microorganisms approach their theoretical maximum, metabolic engineering requires new tools, and approaches for improvements beyond what traditional strategies can achieve. Engineering metabolite dynamics and metabolite heterogeneity is necessary to achieve further improvements in product titers, productivities, and yields. Metabolite dynamics, the ensemble change in metabolite concentration over time, arise from the need for microbes to adapt their metabolism in response to the extracellular environment and are important for controlling growth and productivity in industrial fermentations. Metabolite heterogeneity, the cell-to-cell variation in a metabolite concentration in an isoclonal population, has a significant impact on ensemble productivity. Recent advances in single cell analysis enable a more complete understanding of the processes driving metabolite heterogeneity and reveal metabolic engineering targets. The authors present an overview of the mechanistic origins of metabolite dynamics and heterogeneity, why they are important, their potential effects in chemical production processes, and tools and strategies for engineering metabolite dynamics and heterogeneity. The authors emphasize that the ability to control metabolite dynamics and heterogeneity will bring new avenues of engineering to increase productivity of microbial strains. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intratumor and Intertumor Heterogeneity in Melanoma.

Science.gov (United States)

Grzywa, Tomasz M; Paskal, Wiktor; Włodarski, Paweł K

2017-12-01

Melanoma is a cancer that exhibits one of the most aggressive and heterogeneous features. The incidence rate escalates. A high number of clones harboring various mutations contribute to an exceptional level of intratumor heterogeneity of melanoma. It also refers to metastases which may originate from different subclones of primary lesion. Such component of the neoplasm biology is termed intertumor and intratumor heterogeneity. These levels of tumor heterogeneity hinder accurate diagnosis and effective treatment. The increasing number of research on the topic reflects the need for understanding limitation or failure of contemporary therapies. Majority of analyses concentrate on mutations in cancer-related genes. Novel high-throughput techniques reveal even higher degree of variations within a lesion. Consolidation of theories and researches indicates new routes for treatment options such as targets for immunotherapy. The demand for personalized approach in melanoma treatment requires extensive knowledge on intratumor and intertumor heterogeneity on the level of genome, transcriptome/proteome, and epigenome. Thus, achievements in exploration of melanoma variety are described in details. Particularly, the issue of tumor heterogeneity or homogeneity given BRAF mutations is discussed. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity

Energy Technology Data Exchange (ETDEWEB)

Wang, Li [Pennsylvania State Univ., State College, PA (United States); Li, Li [Pennsylvania State Univ., State College, PA (United States)

2015-10-22

The natural subsurface is highly heterogeneous with minerals distributed in different spatial patterns. Fundamental understanding of how mineral spatial distribution patterns regulate sorption process is important for predicting the transport and fate of chemicals. Existing studies about the sorption was carried out in well-mixed batch reactors or uniformly packed columns, with few data available on the effects of spatial heterogeneities. As a result, there is a lack of data and understanding on how spatial heterogeneities control sorption processes. In this project, we aim to understand and develop modeling capabilities to predict the sorption of Cr(VI), an omnipresent contaminant in natural systems due to its natural occurrence and industrial utilization. We systematically examine the role of spatial patterns of illite, a common clay, in determining the extent of transport limitation and scaling effects associated with Cr(VI) sorption capacity and kinetics using column experiments and reactive transport modeling. Our results showed that the sorbed mass and rates can differ by an order of magnitude due to of the illite spatial heterogeneities and transport limitation. With constraints from data, we also developed the capabilities of modeling Cr(VI) in heterogeneous media. The developed model is then utilized to understand the general principles that govern the relationship between sorption and connectivity, a key measure of the spatial pattern characteristics. This correlation can be used to estimate Cr(VI) sorption characteristics in heterogeneous porous media. Insights gained here bridge gaps between laboratory and field application in hydrogeology and geochemical field, and advance predictive understanding of reactive transport processes in the natural heterogeneous subsurface. We believe that these findings will be of interest to a large number of environmental geochemists and engineers, hydrogeologists, and those interested in contaminant fate and transport

Understanding Heterogeneity and Permeability of Brain Metastases in Murine Models of HER2-Positive Breast Cancer Through Magnetic Resonance Imaging: Implications for Detection and Therapy

Directory of Open Access Journals (Sweden)

Donna H. Murrell

2015-06-01

Full Text Available OBJECTIVES: Brain metastases due to breast cancer are increasing, and the prognosis is poor. Lack of effective therapy is attributed to heterogeneity of breast cancers and their resulting metastases, as well as impermeability of the blood–brain barrier (BBB, which hinders delivery of therapeutics to the brain. This work investigates three experimental models of HER2+ breast cancer brain metastasis to better understand the inherent heterogeneity of the disease. We use magnetic resonance imaging (MRI to quantify brain metastatic growth and explore its relationship with BBB permeability. DESIGN: Brain metastases due to breast cancer cells (SUM190-BR3, JIMT-1-BR3, or MDA-MB-231-BR-HER2 were imaged at 3 T using balanced steady-state free precession and contrast-enhanced T1-weighted spin echo sequences. The histology and immunohistochemistry corresponding to MRI were also analyzed. RESULTS: There were differences in metastatic tumor appearance by MRI, histology, and immunohistochemistry (Ki67, CD31, CD105 across the three models. The mean volume of an MDA-MB-231-BR-HER2 tumor was significantly larger compared to other models (F2,12 = 5.845, P < .05; interestingly, this model also had a significantly higher proportion of Gd-impermeable tumors (F2,12 = 22.18, P < .0001. Ki67 staining indicated that Gd-impermeable tumors had significantly more proliferative nuclei compared to Gd-permeable tumors (t[24] = 2.389, P < .05 in the MDA-MB-231-BR-HER2 model. CD31 and CD105 staining suggested no difference in new vasculature patterns between permeable and impermeable tumors in any model. CONCLUSION: Significant heterogeneity is present in these models of brain metastases from HER2+ breast cancer. Understanding this heterogeneity, especially as it relates to BBB permeability, is important for improvement in brain metastasis detection and treatment delivery.

"Holes" in Student Understanding: Addressing Prevalent Misconceptions regarding Atmospheric Environmental Chemistry

Science.gov (United States)

Kerr, Sara C.; Walz, Kenneth A.

2007-01-01

There is a misconception among undergraduate students that global warming is caused by holes in the ozone layer. In this study, we evaluated the presence of this and other misconceptions surrounding atmospheric chemistry that are responsible for the entanglement of the greenhouse effect and the ozone hole in students' conceptual frameworks. We…

Gas Phase Sulfur, Chlorine and Potassium Chemistry in Biomass Combustion

DEFF Research Database (Denmark)

Løj, Lusi Hindiyarti

2007-01-01

Gas Phase Sulfur, Chlorine and Alkali Metal Chemistry in Biomass Combustion Concern about aerosols formation, deposits, corrosion, and gaseous emissions during biomass combustion, especially straw, continues to be a driving force for investigation on S, Cl, K-containing species under combustions...... conditions. These trace species contained in the biomass structure will be released to the gas phase during combustion and contribute to the problems generated during the process. The investigation during this PhD project is done to stepwise improve the understanding in the chemistry and reduce...... the uncertainties. In the present work, the detailed kinetic model for gas phase sulfur, chlorine, alkali metal, and their interaction has been updated. The K/O/H/Cl chemistry, S chemistry, and their interaction can reasonably predict a range of experimental data. In general, understanding of the interaction...

Integrating UNESCO ICT-Based Instructional Materials in Chemistry Lessons

Directory of Open Access Journals (Sweden)

CHARLIE P. NACARIO

2014-08-01

Full Text Available This study determined the effectiveness of the lessons in Chemistry integrating UNESCO ICT-based instructional material on the achievement of Chemistry students at Central Bicol State University of Agriculture. It aimed to identify lessons that may be developed integrating UNESCO ICT-based instructional materials, determine the effect of the developed lessons using the material on: conceptual understanding; science process skills; and attitude towards chemistry and gather insights from the experiences of the students and teacher. The study used the single group pretest and posttest experimental design. Descriptive, quantitative and qualitative techniques were also utilized. Quantitative data were taken from the pretest-posttest results on the Test on Conceptual Understanding, Science Process Skills and Chemistry Attitudinaire. Qualitative data were drawn from the experts’ assessment of the developed lessons and research instruments, and the insights of students and teacher. The developed lessons integrating UNESCO ICT-based instructional materials were Atomic Model and Structure, Periodic Table of Elements, Chemical Bonding, and Balancing Chemical Equation. These lessons increased the conceptual understanding of the students by topic and skill from very low mastery to average mastery level. The students have slightly improved along the different science process skills. After teaching the lessons, the students’ attitude also improved. The students became more motivated and interested in Chemistry and the lessons were student centered and entailed teacher’s competence and flexibility in computer use.

Interstellar chemistry.

Science.gov (United States)

Klemperer, William

2006-08-15

In the past half century, radioastronomy has changed our perception and understanding of the universe. In this issue of PNAS, the molecular chemistry directly observed within the galaxy is discussed. For the most part, the description of the molecular transformations requires specific kinetic schemes rather than chemical thermodynamics. Ionization of the very abundant molecular hydrogen and atomic helium followed by their secondary reactions is discussed. The rich variety of organic species observed is a challenge for complete understanding. The role and nature of reactions involving grain surfaces as well as new spectroscopic observations of interstellar and circumstellar regions are topics presented in this special feature.

Using Physics Principles in the Teaching of Chemistry.

Science.gov (United States)

Gulden, Warren

1996-01-01

Presents three examples that show how students can use traditional physics principles or laws for the purpose of understanding chemistry better. Examples include Coulomb's Law and melting points, the Faraday Constant, and the Rydberg Constant. Presents a list of some other traditional topics in a chemistry course that could be enhanced by the…

Understanding `green chemistry' and `sustainability': an example of problem-based learning (PBL)

Science.gov (United States)

Günter, Tuğçe; Akkuzu, Nalan; Alpat, Şenol

2017-10-01

Background: This study uses problem-based learning (PBL) to ensure that students comprehend the significance of green chemistry better by experiencing the stages of identifying the problem, developing hypotheses, and providing solutions within the problem-solving process.

Metabolomics analysis of postharvest ripening heterogeneity of ‘Hass' avocadoes

NARCIS (Netherlands)

Pedreschi, R.; Munoz, P.; Robledo, P.; Becerra, C.; Defilippi, B.G.; Eekelen, van H.D.L.M.; Mumm, R.; Westra, E.H.; Vos, de R.C.H.

2014-01-01

The complex physiology of ‘Hass’ avocado renders its postharvest ripening heterogeneous and unpre-dictable. Several approaches have previously been undertaken to broaden our understanding of the causesof this postharvest ripening heterogeneity but without much success. In this study, a fruit biopsy

Seventh BES [Basic Energy Sciences] catalysis and surface chemistry research conference

International Nuclear Information System (INIS)

1990-03-01

Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases

Seventh BES (Basic Energy Sciences) catalysis and surface chemistry research conference

Energy Technology Data Exchange (ETDEWEB)

1990-03-01

Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases. (CBS)

Introduction to nuclear chemistry

International Nuclear Information System (INIS)

Lieser, K.H.

1980-01-01

The study in this book begins with the periodic system of elements (chapter 1). The physical fundamentals necessary to understand nuclear chemistry are dealt with in chapter 2. Chapter 3 and 4 treat the influence of the mass number on the chemical behaviour (isotope effect) and the isotope separation methods thus based on this effect. A main topic is studied in chapter 5, the laws of radioactive decay, a second main topic is dealt with in chapter 8, nuclear reactions. The chemical effects of nuclear reactions are treated on their own chapter 9. Radiochemical reactions which are partly closely linked to the latter are only briefly discussed in chapter 10. The following chapters discuss the various application fields of nuclear chemistry. The large apparatus indispensable for nuclear chemistry is dealt with in a special chapter (chapter 12). Chapter 15 summarizes the manifold applications. (orig.) [de

Nanoparticles found in superheated steam: a quantitative analysis of possible heterogeneous condensation nuclei

Czech Academy of Sciences Publication Activity Database

Kolovratník, M.; Hrubý, Jan; Ždímal, Vladimír; Bartoš, Ondřej; Jiříček, I.; Moravec, Pavel; Zíková, Naděžda

2014-01-01

Roč. 228, č. 2 (2014), s. 186-193 ISSN 0957-6509 R&D Projects: GA ČR GA101/09/1633 Institutional support: RVO:61388998 ; RVO:67985858 Keywords : heterogeneous nucleation * steam turbine * ultrafine aerosol particles Subject RIV: BJ - Thermodynamics; CF - Physical ; Theoretical Chemistry (UCHP-M) Impact factor: 0.645, year: 2014 http://pia.sagepub.com/content/early/2013/12/10/0957650913512816

A study of how precursor key concepts for organic chemistry success are understood by general chemistry students

Science.gov (United States)

Meyer, Patrick Gerard

This study examines college student understanding of key concepts that will support future organic chemistry success as determined by university instructors. During four one-hour individual interviews the sixteen subjects attempted to solve general chemistry problems. A think-aloud protocol was used along with a whiteboard where the students could draw and illustrate their ideas. The protocols for the interviews were adapted from the Covalent Structure and Bonding two-tiered multiple choice diagnostic instrument (Peterson, Treagust, & Garnett, 1989) and augmented by the Geometry and Polarity of Molecules single-tiered multiple choice instrument (Furio & Calatayud, 1996). The interviews were videotaped, transcribed, and coded for analysis to determine the subjects' understanding of the key ideas. The subjects displayed many misconceptions that were summarized into nine assertions about student conceptualization of chemistry. (1) Many students misunderstand the location and nature of intermolecular forces. (2) Some think electronegativity differences among atoms in a molecule are sufficient to make the molecule polar, regardless of spatial arrangement. (3) Most know that higher phase change temperatures imply stronger intermolecular attractions, but many do not understand the difference between covalent molecular and covalent network substances. (4) Many have difficulty deciding whether a molecule is polar or non-polar, often confusing bilateral symmetry with spatial symmetry in all three dimensions. (5) Many cannot reliably draw correct Lewis structures due to carelessness and overuse of flawed algorithms. (6) Many are confused by how electrons can both repel one other and facilitate bonding between atoms via orbitals---this seems oxymoronic to them. (7) Many cannot explain why the atoms of certain elements do not follow the octet rule and some believe the octet rule alone can determine the shape of a molecule. (8) Most do know that electronegativity and polarity

Chemistry between the stars

International Nuclear Information System (INIS)

Kroto, H.W.

1986-01-01

During the past 15 years the techniques used by chemists to determine accurate molecular structures have combined with those of radio astronomers to probe the space between the stars. Together they paint a new picture of interstellar space, a picture which shows that vast clouds of gas and dust are continually collapsing to form stars and planets and that the main constituents of these clouds are molecules, some of which are quite complex organic species. It is now known that many of the organic building blocks, useful in the evolution of biologically significant macromolecules, existed long before the Earth was formed. These findings present a challenge to previous widely-accepted theories that such molecules were first generated in the Earth's primaeval atmosphere. In this paper certain aspects of these discoveries are considered with particular emphasis on the contributions made by techniques of use in general chemistry. After a brief astronomical introduction to the Interstellar Medium (ISM) the interaction between chemistry and radioastronomy is discussed. This is followed by details of some exciting, new and quite unexpected advances in our understanding of carbon chemistry, discovered during experiments aimed at understanding some of the more perplexing radioastronomy results. Finally an overview is given of the present knowledge of the molecular composition of the ISM and the resulting implications in so far as the origins of life are concerned. (author)

Chemistry between the stars

Energy Technology Data Exchange (ETDEWEB)

Kroto, H W

1986-01-01

During the past 15 years the techniques used by chemists to determine accurate molecular structures have combined with those of radio astronomers to probe the space between the stars. Together they paint a new picture of interstellar space, a picture which shows that vast clouds of gas and dust are continually collapsing to form stars and planets and that the main constituents of these clouds are molecules, some of which are quite complex organic species. It is now known that many of the organic building blocks, useful in the evolution of biologically significant macromolecules, existed long before the Earth was formed. These findings present a challenge to previous widely-accepted theories that such molecules were first generated in the Earth's primaeval atmosphere. In this paper certain aspects of these discoveries are considered with particular emphasis on the contributions made by techniques of use in general chemistry. After a brief astronomical introduction to the Interstellar Medium (ISM) the interaction between chemistry and radioastronomy is discussed. This is followed by details of some exciting, new and quite unexpected advances in our understanding of carbon chemistry, discovered during experiments aimed at understanding some of the more perplexing radioastronomy results. Finally an overview is given of the present knowledge of the molecular composition of the ISM and the resulting implications in so far as the origins of life are concerned.

Chemistry for environmental scientists

International Nuclear Information System (INIS)

Moeller, Detlev

2015-01-01

Non-chemists in environmental sciences and engineering (e.g. physicists, biologists, ecologists, geographers, soil scientists, hydrologists, meteorologists, economists, engineers) need chemical basic knowledge for understanding chemical processes in the environment. This book focuses on general and fundamental chemistry (including required physics) such as properties and bonding of matter, chemical kinetics and mechanisms, phase and chemical equilibrium, the basic features of air (gases), water (liquids) and soil (solids) and the most important substances and their reactions in the environment. Selected key environmental chemical processes are shortly characterised in the light of multi-component and multiphase chemistry. This book is also useful for chemists who are beginning work on environmental issues.

Chemistry for environmental scientists

Energy Technology Data Exchange (ETDEWEB)

Moeller, Detlev [Brandenburgische Technische Univ., Berlin (Germany). Lehrstuhl fuer Luftchemie und Luftreinhaltung

2015-07-01

Non-chemists in environmental sciences and engineering (e.g. physicists, biologists, ecologists, geographers, soil scientists, hydrologists, meteorologists, economists, engineers) need chemical basic knowledge for understanding chemical processes in the environment. This book focuses on general and fundamental chemistry (including required physics) such as properties and bonding of matter, chemical kinetics and mechanisms, phase and chemical equilibrium, the basic features of air (gases), water (liquids) and soil (solids) and the most important substances and their reactions in the environment. Selected key environmental chemical processes are shortly characterised in the light of multi-component and multiphase chemistry. This book is also useful for chemists who are beginning work on environmental issues.

Atmospheric Chemistry and Air Pollution

Directory of Open Access Journals (Sweden)

Jeffrey S. Gaffney

2003-01-01

Full Text Available Atmospheric chemistry is an important discipline for understanding air pollution and its impacts. This mini-review gives a brief history of air pollution and presents an overview of some of the basic photochemistry involved in the production of ozone and other oxidants in the atmosphere. Urban air quality issues are reviewed with a specific focus on ozone and other oxidants, primary and secondary aerosols, alternative fuels, and the potential for chlorine releases to amplify oxidant chemistry in industrial areas. Regional air pollution issues such as acid rain, long-range transport of aerosols and visibility loss, and the connections of aerosols to ozone and peroxyacetyl nitrate chemistry are examined. Finally, the potential impacts of air pollutants on the global-scale radiative balances of gases and aerosols are discussed briefly.

Handbook of hot atom chemistry

International Nuclear Information System (INIS)

Adloff, J.P.; Matsuura, Tatsuo; Yoshihara, Kenji

1992-01-01

Hot atom chemistry is an increasingly important field, which has contributed significantly to our understanding of many fundamental processes and reactions. Its techniques have become firmly entrenched in numerous disciplines, such as applied physics, biomedical research, and all fields of chemistry. Written by leading experts, this comprehensive handbook encompasses a broad range of topics. Each chapter comprises a collection of stimulating essays, given an in-depth account of the state-of-the-art of the field, and stressing opportunities for future work. An extensive introduction to the whole area, this book provides unique insight into a vast subject, and a clear delineation of its goals, techniques, and recent findings. It also contains detailed discussions of applications in fields as diverse as nuclear medicine, geochemistry, reactor technology, and the chemistry of comets and interstellar grains. (orig.)

Nitrogen Compounds in Radiation Chemistry

International Nuclear Information System (INIS)

Sims, H.E.; Dey, G.R.; Vaudey, C.E.; Peaucelle, C.; Boucher, J.L.; Toulhoat, N.; Bererd, N.; Koppenol, W.H.; Janata, E.; Dauvois, V.; Durand, D.; Legand, S.; Roujou, J.L.; Doizi, D.; Dannoux, A.; Lamouroux, C.

2009-01-01

Water radiolysis in presence of N 2 is probably the topic the most controversy in the field of water radiolysis. It still exists a strong discrepancy between the different reports of ammonia formation by water radiolysis in presence of N 2 and moreover in absence of oxygen there is no agreement on the formation or not of nitrogen oxide like NO 2 - and NO 3 -. These discrepancies come from multiple sources: - the complexity of the reaction mechanisms where nitrogen is involved - the experimental difficulties - and, the irradiation conditions. The aim of the workshop is to capitalize the knowledge needed to go further in simulations and understanding the problems caused (or not) by the presence of nitrogen / water in the environment of radioactive materials. Implications are evident in terms of corrosion, understanding of biological systems and atmospheric chemistry under radiation. Topics covered include experimental and theoretical approaches, application and fundamental researches: - Nitrate and Ammonia in radiation chemistry in nuclear cycle; - NOx in biological systems and atmospheric chemistry; - Formation of Nitrogen compounds in Nuclear installations; - Nitrogen in future power plant projects (Gen4, ITER...) and large particle accelerators. This document gathers the transparencies available for 7 of the presentations given at this workshop. These are: - H.E SIMS: 'Radiation Chemistry of Nitrogen Compounds in Nuclear Power Plant'; - G.R. DEY: 'Nitrogen Compounds Formation in the Radiolysis of Aqueous Solutions'; - C.E. VAUDEY et al.: 'Radiolytic corrosion of nuclear graphite studied with the dedicated gas irradiation cell of IPNL'; - J.L. BOUCHER: 'Roles and biosynthesis of NO in eukaryotes and prokaryotes'; - W.H. KOPPENOL: 'Chemistry of NOx'; - E. JANATA: 'Yield of OH in N 2 O saturated aqueous solution'; - V. DAUVOIS: 'Analytical strategy for the study of radiolysis gases'

A molecular view of heterogeneous catalysis

DEFF Research Database (Denmark)

Christensen, Claus H.; Nørskov, Jens Kehlet

2008-01-01

The establishment of a molecular view of heterogeneous catalysis has been hampered for a number of reasons. There are, however, recent developments, which show that we are now on the way towards reaching a molecular-scale picture of the way solids work as catalysts. By a combination of new...... by enabling a rational design of new catalysts. We illustrate this important development in heterogeneous catalysis by highlighting recent examples of catalyst systems for which it has been possible to achieve such a detailed understanding. In particular, we emphasize examples where this progress has made...

Aerosol Fragmentation Driven by Coupling of Acid-Base and Free-Radical Chemistry in the Heterogeneous Oxidation of Aqueous Citric Acid by OH Radicals.

Science.gov (United States)

Liu, Matthew J; Wiegel, Aaron A; Wilson, Kevin R; Houle, Frances A

2017-08-10

A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous-phase aerosol is how the free-radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH-initiated oxidation of citric acid aerosol at high relative humidity. The reaction scheme, containing both free-radical and acid-base elementary reaction steps with physically validated rate coefficients, accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. The difference between the two reaction channels centers on the reactivity of carboxylic acid groups. Free-radical reactions mainly add functional groups to the carbon skeleton of neutral citric acid, because carboxylic acid moieties deactivate the unimolecular fragmentation of alkoxy radicals. In contrast, the conjugate carboxylate groups originating from acid-base equilibria activate both acyloxy radical formation and carbon-carbon bond scission of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxalic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and accelerates the substantial water uptake and volume growth that accompany oxidation. These results frame the oxidative lifecycle of atmospheric aerosol: it is governed by feedbacks between reactions that first increase the particle oxidation state, then eventually promote water uptake and acid-base chemistry. When coupled to free-radical reactions, acid-base channels lead to formation of low molecular

Pre-Service Physics and Chemistry Teachers' Conceptual Integration of Physics and Chemistry Concepts

Science.gov (United States)

Tuysuz, Mustafa; Bektas, Oktay; Geban, Omer; Ozturk, Gokhan; Yalvac, Bugrahan

2016-01-01

This study examines the pre-service teachers' opinions about conceptual integration (CI) and their understanding of it. A qualitative phenomenology design was used in the study. Data was collected through in-depth semi-structured interviews comprising ten guiding questions. Three pre-service physics and three pre-service chemistry teachers…

Computer assisted instruction in the general chemistry laboratory

Science.gov (United States)

Pate, Jerry C.

This dissertation examines current applications concerning the use of computer technology to enhance instruction in the general chemistry laboratory. The dissertation critiques widely-used educational software, and explores examples of multimedia presentations such as those used in beginning chemistry laboratory courses at undergraduate and community colleges. The dissertation describes a prototype compact disc (CD) used to (a) introduce the general chemistry laboratory, (b) familiarize students with using chemistry laboratory equipment, (c) introduce laboratory safety practices, and (d) provide approved techniques for maintaining a laboratory notebook. Upon completing the CD portion of the pre-lab, students are linked to individual self-help (WebCT) quizzes covering the information provided on the CD. The CD is designed to improve student understanding of basic concepts, techniques, and procedures used in the general chemistry laboratory.

Iodine chemistry in a reactor regulation

Energy Technology Data Exchange (ETDEWEB)

Powers, D A [Nuclear Regulatory Commission, Washington, DC (United States). Advisory Committee on Reactor Safeguards

1996-12-01

Radioactive iodine has always been an important consideration in the regulation of nuclear power reactors to assure the health and safety of the public. Regulators adopted conservatively bounding predictions of iodine behavior in the earliest days of the development of nuclear power because there was so little known about either accidents or the chemistry of iodine. Today there is a flood of new information and understanding of the chemistry of iodine under reactor accident conditions. This paper offers some thoughts on how the community of scientists engaged in the study of iodine chemistry can present the results of their work so that it is more immediately adopted by the regulator. It is suggested that the scientific community consider the concept of consensus standards so effectively used within the engineering community to define the status of the study of radioactive iodine chemistry for reactor safety. (author) 9 refs.

Iodine chemistry in a reactor regulation

International Nuclear Information System (INIS)

Powers, D.A.

1996-01-01

Radioactive iodine has always been an important consideration in the regulation of nuclear power reactors to assure the health and safety of the public. Regulators adopted conservatively bounding predictions of iodine behavior in the earliest days of the development of nuclear power because there was so little known about either accidents or the chemistry of iodine. Today there is a flood of new information and understanding of the chemistry of iodine under reactor accident conditions. This paper offers some thoughts on how the community of scientists engaged in the study of iodine chemistry can present the results of their work so that it is more immediately adopted by the regulator. It is suggested that the scientific community consider the concept of consensus standards so effectively used within the engineering community to define the status of the study of radioactive iodine chemistry for reactor safety. (author) 9 refs

Terminology dictionary for physics and chemistry

International Nuclear Information System (INIS)

Kim, Jong Deuk

1988-03-01

This book introduces as many as terms covering from basic chemistry and applied chemistry to general industry and tries to explain them correctly. If it is not needed to explain the terms or they are not general, it omits explanation. However, it accurately and precisely, without omitting, describes elementary reaction and operation, representative materials, naming, idiom, and method of measurement. It also adds to supplement all the materials which are helpful in daily lives and are convenient to studying and understanding.

Scientific projection paper for radiation chemistry

International Nuclear Information System (INIS)

Simic, M.G.

1980-01-01

Together with radiation physics, an understanding of radiation chemistry is necessary for full appreciation of biological effects of high and low energy radiations, and for the development of prophylactic, therapeutic and potentiating methods and techniques in biological organisms. Areas covered in some detail in this report include: the early chemical events involved in the deposition of radiation energy; the kinetics of free radical and excited state reactions; the application of radiation chemistry to radiation biology; and the availability of instrumentation

The failure rate dynamics in heterogeneous populations

International Nuclear Information System (INIS)

Cha, Ji Hwan; Finkelstein, Maxim

2013-01-01

Most populations encountered in real world are heterogeneous. In reliability applications, the mixture (observed) failure rate, obviously, can be considered as a measure of ‘average’ quality in these populations. However, in addition to this average measure, some variability characteristics for failure rates can be very helpful in describing the time-dependent changes in quality of heterogeneous populations. In this paper, we discuss variance and the coefficient of variation of the corresponding random failure rate as variability measures for items in heterogeneous populations. Furthermore, there is often a risk that items of poor quality are selected for important missions. Therefore, along with the ‘average quality’ of a population, more ‘conservative’ quality measures should be also defined and studied. For this purpose, we propose the percentile and the tail-mixture of the failure rates as the corresponding conservative measures. Some illustrative examples are given. -- Highlights: ► This paper provides the insight on the variability measures in heterogeneous populations. ► The conservative quality measures in heterogeneous populations are defined. ► The utility of these measures is illustrated by meaningful examples. ► This paper provides a better understanding of the dynamics in heterogeneous populations

Fission product chemistry in severe nuclear reactor accidents

International Nuclear Information System (INIS)

Nichols, A.L.

1990-09-01

A specialist's meeting was held at JRC-Ispra from 15 to 17 January 1990 to review the current understanding of fission-product chemistry during severe accidents in light water reactors. Discussions focussed on the important chemical phenomena that could occur across the wide range of conditions of a damaged nuclear plant. Recommendations for future chemistry work were made covering the following areas: (a) fuel degradation and fission-product release, (b) transport and attenuation processes in the reactor coolant system, (c) containment chemistry (iodine behaviour and core-concrete interactions)

The radiation chemistry of heterogeneous and homogeneous nitrogen and water systems

International Nuclear Information System (INIS)

Linacre, J.K.; Marsh, W.R.

1981-06-01

Measurements were made of the radiation chemical products such as nitric acid formed when nitrogen gas mixtures in the presence of water vapour and liquid were irradiated with the mixed neutron/gamma field of the BEPO reactor to doses of ca 10 21 to 10 23 eVg -1 . The water was analysed for NO 3 - , NO 2 - and NH 4 + ions, also for H 2 O 2 , NH 2 OH and N 2 H 4 . The investigation was aimed at obtaining information relevant to the DIDO and PLUTO reactors, but the results are of more general interest. The results are discussed in terms of reactions to be expected, especially those of N atoms, and are compared with those of other work on radiation and gas discharge chemistry. (author)

Polymerization of aliphatic alkynes with heterogeneous Mo catalysts supported on mesoporous molecular sieves

Czech Academy of Sciences Publication Activity Database

Balcar, Hynek; Topka, Pavel; Sedláček, J.; Zedník, J.; Čejka, Jiří

2008-01-01

Roč. 46, č. 7 (2008), s. 2593-2599 ISSN 0887-624X R&D Projects: GA ČR GA203/05/2194; GA AV ČR IAA4040411; GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : alkyne polymerization * conjugated polymers * metathesis * Mo heterogeneous catalysts Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.821, year: 2008

Quantum-dot-based immunofluorescent imaging of HER2 and ER provides new insights into breast cancer heterogeneity

International Nuclear Information System (INIS)

Chen Chuang; Li Yan; Peng Jun; Xu Hao; Tang Hongwu; Zhang Zhiling; Pang Daiwen; Xia Heshun; Wu Qiongshui; Zeng Libo; Zhu Xiaobo

2010-01-01

Breast cancer (BC) is a heterogeneous tumor, and better understanding of its heterogeneity is essential to improving treatment effect. Quantum dot (QD)-based immunofluorescent nanotechnology (QD-IHC) for molecular pathology has potential advantages in delineating tumor heterogeneity. This potential is explored in this paper by QD-IHC imaging of HER2 and ER. BC heterogeneity can be displayed more clearly and sensitively by QD-IHC than conventional IHC in BC tissue microarrays. Furthermore, the simultaneous imaging of ER and HER2 might help understand their interactions during the process of evolution of heterogeneous BC.

Fundamental concepts in heterogeneous catalysis

CERN Document Server

Norskov, Jens K; Abild-Pedersen, Frank; Bligaard, Thomas

2014-01-01

This book is based on a graduate course and suitable as a primer for any newcomer to the field, this book is a detailed introduction to the experimental and computational methods that are used to study how solid surfaces act as catalysts.   Features include:First comprehensive description of modern theory of heterogeneous catalysisBasis for understanding and designing experiments in the field   Allows reader to understand catalyst design principlesIntroduction to important elements of energy transformation technologyTest driven at Stanford University over several semesters

Robust mechanobiological behavior emerges in heterogeneous myosin systems

Science.gov (United States)

Egan, Paul F.; Moore, Jeffrey R.; Ehrlicher, Allen J.; Weitz, David A.; Schunn, Christian; Cagan, Jonathan; LeDuc, Philip

2017-09-01

Biological complexity presents challenges for understanding natural phenomenon and engineering new technologies, particularly in systems with molecular heterogeneity. Such complexity is present in myosin motor protein systems, and computational modeling is essential for determining how collective myosin interactions produce emergent system behavior. We develop a computational approach for altering myosin isoform parameters and their collective organization, and support predictions with in vitro experiments of motility assays with α-actinins as molecular force sensors. The computational approach models variations in single myosin molecular structure, system organization, and force stimuli to predict system behavior for filament velocity, energy consumption, and robustness. Robustness is the range of forces where a filament is expected to have continuous velocity and depends on used myosin system energy. Myosin systems are shown to have highly nonlinear behavior across force conditions that may be exploited at a systems level by combining slow and fast myosin isoforms heterogeneously. Results suggest some heterogeneous systems have lower energy use near stall conditions and greater energy consumption when unloaded, therefore promoting robustness. These heterogeneous system capabilities are unique in comparison with homogenous systems and potentially advantageous for high performance bionanotechnologies. Findings open doors at the intersections of mechanics and biology, particularly for understanding and treating myosin-related diseases and developing approaches for motor molecule-based technologies.

Advanced radiation chemistry research: Current status

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-10-01

Radiation chemistry is a branch of chemistry that studies chemical transformations in materials exposed to high-energy radiations. It is based on the use of ionizing radiation as the initiator or catalyst in chemical reactions. The most significant advantage of radiation chemistry lies in its ability to be used in the production and study of almost any reactive atomic and molecular species playing a part in chemical reaction, synthesis, industrial processes, or in biological systems. Over the the last few years a number of meetings have taken place, under the auspices of the IAEA, in order to evaluate recent developments in radiation chemistry as well as the trends indicated by the results obtained. Radiation chemists from different countries have participated at these meetings. The present publication, a companion to the previous publication - New Trends and Development in Radiation Chemistry, IAEA-TECDOC-527 (1989) - includes some of the important contributions presented at these meetings. It is hoped that it will provide a useful overview of current activities and of emerging trends in this field, thus promoting better understanding of potential contributions of radiation chemistry to other fields of knowledge as well as to practical applications in industry, medicine and agriculture. Refs, figs and tabs.

Advanced radiation chemistry research: Current status

International Nuclear Information System (INIS)

1995-10-01

Radiation chemistry is a branch of chemistry that studies chemical transformations in materials exposed to high-energy radiations. It is based on the use of ionizing radiation as the initiator or catalyst in chemical reactions. The most significant advantage of radiation chemistry lies in its ability to be used in the production and study of almost any reactive atomic and molecular species playing a part in chemical reaction, synthesis, industrial processes, or in biological systems. Over the the last few years a number of meetings have taken place, under the auspices of the IAEA, in order to evaluate recent developments in radiation chemistry as well as the trends indicated by the results obtained. Radiation chemists from different countries have participated at these meetings. The present publication, a companion to the previous publication - New Trends and Development in Radiation Chemistry, IAEA-TECDOC-527 (1989) - includes some of the important contributions presented at these meetings. It is hoped that it will provide a useful overview of current activities and of emerging trends in this field, thus promoting better understanding of potential contributions of radiation chemistry to other fields of knowledge as well as to practical applications in industry, medicine and agriculture. Refs, figs and tabs

Catalysis as a foundational pillar of green chemistry

Energy Technology Data Exchange (ETDEWEB)

Anastas, Paul T. [White House Office of Science and Technology Policy, Department of Chemistry, University of Nottingham Nottingham, (United Kingdom); Kirchhoff, Mary M. [U.S. Environmental Protection Agency and Trinity College, Washington, DC (United States); Williamson, Tracy C. [U.S. Environmental Protection Agency, Washington, DC (United States)

2001-11-30

are serving as a strong incentive to industry to adopt greener technologies. Developing green chemistry methodologies is a challenge that may be viewed through the framework of the Twelve Principles of Green Chemistry . These principles identify catalysis as one of the most important tools for implementing green chemistry. Catalysis offers numerous green chemistry benefits including lower energy requirements, catalytic versus stoichiometric amounts of materials, increased selectivity, and decreased use of processing and separation agents, and allows for the use of less toxic materials. Heterogeneous catalysis, in particular, addresses the goals of green chemistry by providing the ease of separation of product and catalyst, thereby eliminating the need for separation through distillation or extraction. In addition, environmentally benign catalysts such as clays and zeolites, may replace more hazardous catalysts currently in use. This paper highlights a variety of ways in which catalysis may be used as a pollution prevention tool in green chemistry reactions. The benefits to human health, environment, and the economic goals realized through the use of catalysis in manufacturing and processing are illustrated by focusing on the catalyst design and catalyst applications.

The Effect of Chemistry Laboratory Activities on Students' Chemistry Perception and Laboratory Anxiety Levels

Science.gov (United States)

Aydogdu, Cemil

2017-01-01

Chemistry lesson should be supported with experiments to understand the lecture effectively. For safety laboratory environment and to prevent laboratory accidents; chemical substances' properties, working principles for chemical substances' usage should be learnt. Aim of the present study was to analyze the effect of experiments which depend on…

Understanding "Green Chemistry" and "Sustainability": An Example of Problem-Based Learning (PBL)

Science.gov (United States)

Günter, Tugçe; Akkuzu, Nalan; Alpat, Senol

2017-01-01

Background: This study uses problem-based learning (PBL) to ensure that students comprehend the significance of green chemistry better by experiencing the stages of identifying the problem, developing hypotheses, and providing solutions within the problem-solving process. Purpose: The aim of this study is to research the effect of PBL implemented…

Who Says Organic Chemistry Is Difficult? Exploring Perspectives and Perceptions

Science.gov (United States)

O'Dwyer, Anne; Childs, Peter E.

2017-01-01

Much research has identified organic chemistry as an area of difficulty for learners. There is also much literature pertaining to the factors that contribute to learners' difficulties. This paper explores the intersections of teachers' and learners' perceptions of teaching and learning organic chemistry respectively. Understanding these nuances…

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

Science.gov (United States)

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.

Chemistry and cosmology.

Science.gov (United States)

Black, John H

2006-01-01

The simplest elements, hydrogen and helium, offer a remarkably rich chemistry, which has controlled crucial features of the early evolution of the universe. Theoretical models of the origin of structure (stars, galaxies, clusters of galaxies, etc.) now incorporate this chemistry in some detail. In addition to the origin of structure, cosmologists are concerned with observational tests of competing world models. Primordial chemistry may give rise to some of the earliest departures from thermodynamic equilibrium in the universe. These effects may be observable as broad-band spectroscopic distortions of the cosmic background radiation, which otherwise exhibits a nearly perfect blackbody spectrum. The chemical history of the expanding universe is followed through a detailed calculation of the evolution of the abundances of H, H+, H-, H2, H2+, H3+, and other minor species. It is shown that continuous absorption by the small concentration of H- can produce a distortion in the cosmic background spectrum with a maximum at a frequency near nu/c = 9 cm-1 (wavelength 1.1 mm). The predicted effect lies only a factor of 5 below current limits. Its detection would provide an important test of our understanding of the recombination epoch of the universe.

Measuring Meaningful Learning in the Undergraduate General Chemistry and Organic Chemistry Laboratories: A Longitudinal Study

Science.gov (United States)

Galloway, Kelli R.; Bretz, Stacey Lowery

2015-01-01

Understanding how students learn in the undergraduate chemistry teaching laboratory is an essential component to developing evidence-based laboratory curricula. The Meaningful Learning in the Laboratory Instrument (MLLI) was developed to measure students' cognitive and affective expectations and experiences for learning in the chemistry…

Probing the structure of heterogeneous diluted materials by diffraction tomography.

Science.gov (United States)

Bleuet, Pierre; Welcomme, Eléonore; Dooryhée, Eric; Susini, Jean; Hodeau, Jean-Louis; Walter, Philippe

2008-06-01

The advent of nanosciences calls for the development of local structural probes, in particular to characterize ill-ordered or heterogeneous materials. Furthermore, because materials properties are often related to their heterogeneity and the hierarchical arrangement of their structure, different structural probes covering a wide range of scales are required. X-ray diffraction is one of the prime structural methods but suffers from a relatively poor detection limit, whereas transmission electron analysis involves destructive sample preparation. Here we show the potential of coupling pencil-beam tomography with X-ray diffraction to examine unidentified phases in nanomaterials and polycrystalline materials. The demonstration is carried out on a high-pressure pellet containing several carbon phases and on a heterogeneous powder containing chalcedony and iron pigments. The present method enables a non-invasive structural refinement with a weight sensitivity of one part per thousand. It enables the extraction of the scattering patterns of amorphous and crystalline compounds with similar atomic densities and compositions. Furthermore, such a diffraction-tomography experiment can be carried out simultaneously with X-ray fluorescence, Compton and absorption tomographies, enabling a multimodal analysis of prime importance in materials science, chemistry, geology, environmental science, medical science, palaeontology and cultural heritage.

Radiation chemistry in solvent extraction: FY2010 Research

International Nuclear Information System (INIS)

Mincher, Bruce J.; Martin, Leigh R.; Mezyk, Stephen P.

2010-01-01

This report summarizes work accomplished under the Fuel Cycle Research and Development (FCR and D) program in the area of radiation chemistry during FY 2010. The tasks assigned during FY 2010 included: (1) Development of techniques to measure free radical reaction kinetics in the organic phase. (2) Initiation of an alpha-radiolysis program; (3) Initiation of an effort to understand dose rate effects in radiation chemistry; (4) Continued work to characterize TALSPEAK radiation chemistry Progress made on each of these tasks is reported here. Briefly, a method was developed and used to measure the kinetics of the reactions of the NO3 radical with solvent extraction ligands in organic solution, and the method to measure OH radical reactions under the same conditions has been designed. Rate constants for the CMPO and DMDOHEMA reaction with NO3 radical in organic solution are reported. Alpha-radiolysis was initiated on samples of DMDOHEMA in alkane solution using He ion beam irradiation and 211At isotope irradiation. The samples are currently being analyzed for comparison to DMDOHEMA ?-irradiations using a custom-developed mass spectrometric method. Results are also reported for the radiolytic generation of nitrous acid, in ?-irradiated nitric acid. It is shown that the yield of nitrous acid is unaffected by an order-of-magnitude change in dose rate. Finally, recent results for TALSPEAK radiolysis are reported, summarizing the effects on solvent extraction efficiency due to HDEHP irradiation, and the stable products of lactic acid and DTPA irradiation. In addition, results representing increased scope are presented for the radiation chemistry program. These include an investigation of the effect of metal complexation on radical reaction kinetics using DTPA as an example, and the production of a manuscript reporting the mechanism of Cs-7SB radiolysis. The Cs-7SB work takes advantage of recent results from a current LDRD program to understand the fundamental chemistry of

Catalysis as an important tool of green chemistry

Energy Technology Data Exchange (ETDEWEB)

Beletskaya, Irina P [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Kustov, Leonid M [N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow (Russian Federation)

2010-08-12

Published data of the last decade demonstrating the significant achievements in the catalytic synthesis of organic compounds are analyzed from the green chemistry standpoint. It is demonstrated that the use of new catalysts (including nano-sized ones) and solvents (water, ionic liquids, fluorinated derivatives), microwave processes, superctitical and two-phase media, and heterogenized metal complex catalytic systems should be distinguished among the most promising approaches to such processes. The main applications of metal complex systems are considered, in particular, hydrogenation, partial oxidation and cross-coupling reactions, in particular, enantioselective reactions.

Catalysis as an important tool of green chemistry

International Nuclear Information System (INIS)

Beletskaya, Irina P; Kustov, Leonid M

2010-01-01

Published data of the last decade demonstrating the significant achievements in the catalytic synthesis of organic compounds are analyzed from the green chemistry standpoint. It is demonstrated that the use of new catalysts (including nano-sized ones) and solvents (water, ionic liquids, fluorinated derivatives), microwave processes, superctitical and two-phase media, and heterogenized metal complex catalytic systems should be distinguished among the most promising approaches to such processes. The main applications of metal complex systems are considered, in particular, hydrogenation, partial oxidation and cross-coupling reactions, in particular, enantioselective reactions.

Chemistry and Heritage

Science.gov (United States)

Vittoria Barbarulo, Maria

2014-05-01

Chemistry is the central science, as it touches every aspect of the society we live in and it is intertwined with many aspects of our culture; in particular, the strong link between Chemistry and Archaeology and Art History is being explored, offering a penetrating insight into an area of growing interest from an educational point of view. A series of vital and vibrant examples (i.e., ancient bronzes composition, colour changes due to natural pigment decomposition, marble degradation) has been proposed, on one hand, to improve student understanding of the relationship between cultural and scientific issues arising from the examination, the conservation, and the maintenance of cultural Heritage, on the other, to illustrate the role of the underlying Chemistry. In some case studies, a survey of the most relevant atmospheric factors, which are involved in the deterioration mechanisms, has also been presented to the students. First-hand laboratory experiences have been providing an invaluable means of discovering the full and varied world of Chemistry. Furthermore, the promotion of an interdisciplinary investigation of a famous painting or fresco, involving the study of its nature and significance, the definition of its historical context, any related literature, the chemical knowledge of the materials used, may be an excellent occasion to experiment the Content and Language Integrated Learning (CLIL). The aim of this approach is to convey the important message that everyone has the responsibility to care for and preserve Heritage for the benefit of present and future generations.

Variability in chemistry of surface and soil waters of an ...

African Journals Online (AJOL)

Water chemistry is important for the maintenance of wetland structure and function. Interpreting ecological patterns in a wetland system therefore requires an in-depth understanding of the water chemistry of that system. We investigated the spatial distribution of chemical solutes both in soil pore water and surface water, ...

Interactions of Chemistry Teachers with Gifted Students in a Regular High-School Chemistry Classroom

Science.gov (United States)

Benny, Naama; Blonder, Ron

2018-01-01

Regular high-school chemistry teachers view gifted students as one of several types of students in a regular (mixed-ability) classroom. Gifted students have a range of unique abilities that characterize their learning process: mostly they differ in three key learning aspects: their faster learning pace, increased depth of understanding, and…

Titan: a laboratory for prebiological organic chemistry

Science.gov (United States)

Sagan, C.; Thompson, W. R.; Khare, B. N.

1992-01-01

When we examine the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), the satellites in the outer solar system, comets, and even--through microwave and infrared spectroscopy--the cold dilute gas and grains between the stars, we find a rich organic chemistry, presumably abiological, not only in most of the solar system but throughout the Milky Way galaxy. In part because the composition and surface pressure of the Earth's atmosphere 4 x 10(9) years ago are unknown, laboratory experiments on prebiological organic chemistry are at best suggestive; but we can test our understanding by looking more closely at the observed extraterrestrial organic chemistry. The present Account is restricted to atmospheric organic chemistry, primarily on the large moon of Saturn. Titan is a test of our understanding of the organic chemistry of planetary atmospheres. Its atmospheric bulk composition (N2/CH4) is intermediate between the highly reducing (H2/He/CH4/NH3/H2O) atmospheres of the Jovian planets and the more oxidized (N2/CO2/H2O) atmospheres of the terrestrial planets Mars and Venus. It has long been recognized that Titan's organic chemistry may have some relevance to the events that led to the origin of life on Earth. But with Titan surface temperatures approximately equal to 94 K and pressures approximately equal to 1.6 bar, the oceans of the early Earth have no ready analogue on Titan. Nevertheless, tectonic events in the water ice-rich interior or impact melting and slow re-freezing may lead to an episodic availability of liquid water. Indeed, the latter process is the equivalent of a approximately 10(3)-year-duration shallow aqueous sea over the entire surface of Titan.

Elastic Rock Heterogeneity Controls Brittle Rock Failure during Hydraulic Fracturing

Science.gov (United States)

Langenbruch, C.; Shapiro, S. A.

2014-12-01

For interpretation and inversion of microseismic data it is important to understand, which properties of the reservoir rock control the occurrence probability of brittle rock failure and associated seismicity during hydraulic stimulation. This is especially important, when inverting for key properties like permeability and fracture conductivity. Although it became accepted that seismic events are triggered by fluid flow and the resulting perturbation of the stress field in the reservoir rock, the magnitude of stress perturbations, capable of triggering failure in rocks, can be highly variable. The controlling physical mechanism of this variability is still under discussion. We compare the occurrence of microseismic events at the Cotton Valley gas field to elastic rock heterogeneity, obtained from measurements along the treatment wells. The heterogeneity is characterized by scale invariant fluctuations of elastic properties. We observe that the elastic heterogeneity of the rock formation controls the occurrence of brittle failure. In particular, we find that the density of events is increasing with the Brittleness Index (BI) of the rock, which is defined as a combination of Young's modulus and Poisson's ratio. We evaluate the physical meaning of the BI. By applying geomechanical investigations we characterize the influence of fluctuating elastic properties in rocks on the probability of brittle rock failure. Our analysis is based on the computation of stress fluctuations caused by elastic heterogeneity of rocks. We find that elastic rock heterogeneity causes stress fluctuations of significant magnitude. Moreover, the stress changes necessary to open and reactivate fractures in rocks are strongly related to fluctuations of elastic moduli. Our analysis gives a physical explanation to the observed relation between elastic heterogeneity of the rock formation and the occurrence of brittle failure during hydraulic reservoir stimulations. A crucial factor for understanding

Third Chemistry Conference on Recent Trends in Chemistry

International Nuclear Information System (INIS)

Saeed, M.M.; Wheed, S.

2011-01-01

The third chemistry conference 2011 on recent trends in chemistry was held from October 17-19, 2001 at Islamabad, Pakistan. More than 65 papers and oral presentation. The scope of the conference was wide open and provides and opportunity for participation of broad spectrum of chemists. This forum provided a platform for the dissemination of the latest research followed by discussion pertaining to new trends in chemistry. This con fence covered different aspects of subjects including analytical chemistry, environmental chemistry, polymer chemistry, industrial chemistry, biochemistry and nano chemistry etc. (A.B.)

Constitutional dynamic chemistry: bridge from supramolecular chemistry to adaptive chemistry.

Science.gov (United States)

Lehn, Jean-Marie

2012-01-01

Supramolecular chemistry aims at implementing highly complex chemical systems from molecular components held together by non-covalent intermolecular forces and effecting molecular recognition, catalysis and transport processes. A further step consists in the investigation of chemical systems undergoing self-organization, i.e. systems capable of spontaneously generating well-defined functional supramolecular architectures by self-assembly from their components, thus behaving as programmed chemical systems. Supramolecular chemistry is intrinsically a dynamic chemistry in view of the lability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibility, so as to allow a continuous change in constitution by reorganization and exchange of building blocks. These features define a Constitutional Dynamic Chemistry (CDC) on both the molecular and supramolecular levels.CDC introduces a paradigm shift with respect to constitutionally static chemistry. The latter relies on design for the generation of a target entity, whereas CDC takes advantage of dynamic diversity to allow variation and selection. The implementation of selection in chemistry introduces a fundamental change in outlook. Whereas self-organization by design strives to achieve full control over the output molecular or supramolecular entity by explicit programming, self-organization with selection operates on dynamic constitutional diversity in response to either internal or external factors to achieve adaptation.The merging of the features: -information and programmability, -dynamics and reversibility, -constitution and structural diversity, points to the emergence of adaptive and evolutive chemistry, towards a chemistry of complex matter.

Innovative Sol-Gel Routes for the Bottom-up Preparation of Heterogeneous Catalysts.

Science.gov (United States)

Debecker, Damien P

2017-12-11

Heterogeneous catalysts can be prepared by different methods offering various levels of control on the final properties of the solid. In this account, we exemplify bottom-up preparation routes that are based on the sol-gel chemistry and allow to tailor some decisive properties of solid catalysts. First, an emulsion templating strategy is shown to lead to macrocellular self-standing monoliths with a macroscopic 3D structure. The latter can be used as catalyst or catalyst supports in flow chemistry, without requiring any subsequent shaping step. Second, the aerosol-assisted sol-gel process allows for the one-step and continuous production of porous mixed oxides. Tailored textural properties can be obtained together with an excellent control on composition and homogeneity. Third, the application of non-hydrolytic sol-gel routes, in the absence of water, leads to mixed oxides with outstanding textural properties and with peculiar surface chemistry. In all cases, the resulting catalytic performance can be correlated with the specificities of the preparation routes presented. This is exemplified in catalytic reactions in the fields of biomass conversion, petro chemistry, enantioselective organic synthesis, and air pollution mitigation. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser-pulsed Plasma Chemistry: Laser-initiated Plasma Oxidation Of Niobium

OpenAIRE

Marks R.F.; Pollak R.A.; Avouris Ph.; Lin C.T.; Thefaine Y.J.

1983-01-01

We report the first observation of the chemical modification of a solid surface exposed to an ambient gas plasma initiated by the interaction of laser radiation with the same surface. A new technique, which we designate laser-pulsed plasma chemistry (LPPC), is proposed for activating heterogeneous chemical reactions at solid surfaces in a gaseous ambient by means of a plasma initiated by laser radiation. Results for niobium metal in one atmosphere oxygen demonstrate single-pulse, self-limitin...

Heterogeneous catalysis : introduction

NARCIS (Netherlands)

Niemantsverdriet, J.W.; Schlögl, R.; Reedijk, J.; Poeppelmeier, K.

2013-01-01

Comprehensive Inorganic Chemistry II reviews and examines topics of relevance to today’s inorganic chemists. Covering more interdisciplinary and high impact areas, Comprehensive Inorganic Chemistry II includes biological inorganic chemistry, solid state chemistry, materials chemistry, and

Transcriptional profiling of dividing tumor cells detects intratumor heterogeneity linked to cell proliferation in a brain tumor model

Czech Academy of Sciences Publication Activity Database

Endaya, B.; Lam, P.Y.P.; Meedeniya, A.C.B.; Neužil, Jiří

2016-01-01

Roč. 10, č. 1 (2016), s. 126-137 ISSN 1574-7891 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:86652036 Keywords : Intratumor heterogeneity * Click chemistry * Proliferation * Gene profiling Subject RIV: FD - Oncology ; Hematology Impact factor: 5.314, year: 2016

Knot theory in modern chemistry.

Science.gov (United States)

Horner, Kate E; Miller, Mark A; Steed, Jonathan W; Sutcliffe, Paul M

2016-11-21

Knot theory is a branch of pure mathematics, but it is increasingly being applied in a variety of sciences. Knots appear in chemistry, not only in synthetic molecular design, but also in an array of materials and media, including some not traditionally associated with knots. Mathematics and chemistry can now be used synergistically to identify, characterise and create knots, as well as to understand and predict their physical properties. This tutorial review provides a brief introduction to the mathematics of knots and related topological concepts in the context of the chemical sciences. We then survey the broad range of applications of the theory to contemporary research in the field.

Micromechanical anisotropy and heterogeneity of the meniscus extracellular matrix.

Science.gov (United States)

Li, Qing; Qu, Feini; Han, Biao; Wang, Chao; Li, Hao; Mauck, Robert L; Han, Lin

2017-05-01

To understand how the complex biomechanical functions of the meniscus are endowed by the nanostructure of its extracellular matrix (ECM), we studied the anisotropy and heterogeneity in the micromechanical properties of the meniscus ECM. We used atomic force microscopy (AFM) to quantify the time-dependent mechanical properties of juvenile bovine meniscus at deformation length scales corresponding to the diameters of collagen fibrils. At this scale, anisotropy in the elastic modulus of the circumferential fibers, the major ECM structural unit, can be attributed to differences in fibril deformation modes: uncrimping when normal to the fiber axis, and laterally constrained compression when parallel to the fiber axis. Heterogeneity among different structural units is mainly associated with their variations in microscale fiber orientation, while heterogeneity across anatomical zones is due to alterations in collagen fibril diameter and alignment at the nanoscale. Unlike the elastic modulus, the time-dependent properties are more homogeneous and isotropic throughout the ECM. These results enable a detailed understanding of the meniscus structure-mechanics at the nanoscale, and can serve as a benchmark for understanding meniscus biomechanical functions, documenting disease progression and designing tissue repair strategies. Meniscal damage is a common cause of joint injury, which can lead to the development of post-traumatic osteoarthritis among young adults. Restoration of meniscus function requires repairing its highly heterogeneous and complex extracellular matrix. Employing AFM, this study quantifies the anisotropic and heterogeneous features of the meniscus ECM structure and mechanics. The micromechanical properties are interpreted within the context of the collagen fibril nanostructure and its variation with tissue anatomical locations. These results provide a fundamental structure-mechanics knowledge benchmark, against which, repair and regeneration strategies can

Dynamical Heterogeneity in Granular Fluids and Structural Glasses

Science.gov (United States)

Avila, Karina E.

Our current understanding of the dynamics of supercooled liquids and other similar slowly evolving (glassy) systems is rather limited. One aspect that is particularly poorly understood is the origin and behavior of the strong non trivial fluctuations that appear in the relaxation process toward equilibrium. Glassy systems and granular systems both present regions of particles moving cooperatively and at different rates from other regions. This phenomenon is known as spatially heterogeneous dynamics. A detailed explanation of this phenomenon may lead to a better understanding of the slow relaxation process, and perhaps it could even help to explain the presence of the glass transition. This dissertation concentrates on studying dynamical heterogeneity by analyzing simulation data for models of granular materials and structural glasses. For dissipative granular fluids, the growing behavior of dynamical heterogeneities is studied for different densities and different degrees of inelasticity in the particle collisions. The correlated regions are found to grow rapidly as the system approaches dynamical arrest. Their geometry is conserved even when probing at different cutoff length in the correlation function or when the energy dissipation in the system is increased. For structural glasses, I test a theoretical framework that models dynamical heterogeneity as originated in the presence of Goldstone modes, which emerge from a broken continuous time reparametrization symmetry. This analysis is based on quantifying the size and the spatial correlations of fluctuations in the time variable and of other kinds of fluctuations. The results obtained here agree with the predictions of the hypothesis. In particular, the fluctuations associated to the time reparametrization invariance become stronger for low temperatures, long timescales, and large coarse graining lengths. Overall, this research points to dynamical heterogeneity to be described for granular systems similarly than

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup

2013-10-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

Analysis of heterogeneous oxygen exchange and fuel oxidation on the catalytic surface of perovskite membranes

KAUST Repository

Hong, Jongsup; Kirchen, Patrick; Ghoniem, Ahmed F.

2013-01-01

The catalytic kinetics of oxygen surface exchange and fuel oxidation for a perovskite membrane is investigated in terms of the thermodynamic state in the immediate vicinity of or on the membrane surface. Perovskite membranes have been shown to exhibit both oxygen perm-selectivity and catalytic activity for hydrocarbon conversion. A fundamental description of their catalytic surface reactions is needed. In this study, we infer the kinetic parameters for heterogeneous oxygen surface exchange and catalytic fuel conversion reactions, based on permeation rate measurements and a spatially resolved physical model that incorporates detailed chemical kinetics and transport in the gas-phase. The conservation equations for surface and bulk species are coupled with those of the gas-phase species through the species production rates from surface reactions. It is shown that oxygen surface exchange is limited by dissociative/associative adsorption/desorption of oxygen molecules onto/from the membrane surface. On the sweep side, while the catalytic conversion of methane to methyl radical governs the overall surface reactions at high temperature, carbon monoxide oxidation on the membrane surface is dominant at low temperature. Given the sweep side conditions considered in ITM reactor experiments, gas-phase reactions also play an important role, indicating the significance of investigating both homogeneous and heterogeneous chemistry and their coupling when examining the results. We show that the local thermodynamic state at the membrane surface should be considered when constructing and examining models of oxygen permeation and heterogeneous chemistry. © 2013 Elsevier B.V.

Radiation chemistry

International Nuclear Information System (INIS)

Rodgers, F.; Rodgers, M.A.

1987-01-01

The contents of this book include: Interaction of ionizing radiation with matter; Primary products in radiation chemistry; Theoretical aspects of radiation chemistry; Theories of the solvated electron; The radiation chemistry of gases; Radiation chemistry of colloidal aggregates; Radiation chemistry of the alkali halides; Radiation chemistry of polymers; Radiation chemistry of biopolymers; Radiation processing and sterilization; and Compound index

Beaver dams maintain fish biodiversity by increasing habitat heterogeneity throughout a low-gradient stream network

Science.gov (United States)

Smith, Joseph M.; Mather, Martha E.

2013-01-01

Understanding the relationship between heterogeneity and biodiversity is an active focus of ecological research. Although habitat heterogeneity is conceptually linked to biodiversity, the amount and configuration of heterogeneity that maintains biodiversity within ecosystems is not well understood, especially for an entire stream network.

Communicating why land surface heterogeneity matters

Science.gov (United States)

Tague, C.; Burke, W.; Bart, R. R.; Turpin, E.; Wood, T.; Gordon, D.

2017-12-01

As hydrologic scientists, we know that land surface heterogeneity can have nuanced and sometimes dramatic impacts on the water cycle. Land surface characteristics, including the structure and composition of vegetation and soil storage and drainage properties, alter how incoming precipitation is translated into streamflow and evapotranspiration. Land surface heterogeneity can explain why this partitioning of incoming precipitation cannot always be computed by a simple water budget calculation. We also know that land surface characteristics are dynamic - vegetation grows and changes with fire, disease and human actions and these changes will alter the partitioning of water - how much so, however depends itself on other site characteristics - soil water storage and the timing and magnitude of precipitation. This complex impact of space-time dynamics on the water cycle is something we need to effectively communicate to non-experts. For example, we may want to explain why sometimes forest management practices increase water availability but sometimes they don't - or why the impacts of urbanization or fire are location specific. If we do not communicate these dependencies we risk over-simplifying and eroding scientific credibility when observed effects don't match simple generalizations. On the other hand excessive detail can overwhelm and disengage audiences. So how do we help different communities public, private landowners, other scientists, NGOs, governments to better understand the role of space-time heterogeneity. To address this issue, we present some results from ongoing work that looks at the impact of fuel treatment of forest ecohydrology. This work stem from a collaboration between an ecohydrologic modeling team, social-scientists, a visual artist and compute graphics students. We use a coupled model, validated with field measurements, to show why spatial heterogeneity matters for understanding the impact of fuel treatments on the water cycle for the Sierra

The coupling effect of gas-phase chemistry and surface reactions on oxygen permeation and fuel conversion in ITM reactors

KAUST Repository

Hong, Jongsup; Kirchen, Patrick; Ghoniem, Ahmed F.

2015-01-01

© 2015 Elsevier B.V. The effect of the coupling between heterogeneous catalytic reactions supported by an ion transport membrane (ITM) and gas-phase chemistry on fuel conversion and oxygen permeation in ITM reactors is examined. In ITM reactors

Moving Green Chemistry Forward: Networks as a Foundation

Science.gov (United States)

Carter, T.; Lough, G.

2014-12-01

Green chemistry is a growing discipline, but for a variety of reasons, it has not yet become integrated into science curriculum and the greater societal conscience. With its increasing economic benefits to many sectors including business, industry, and academia and its potential to make science more accessible not only to science students but also to the general citizenry, we suggested answers to the questions: Why has greater success not been realized? What are the particular barriers to wider implementation? And what are incentives and ways to move green chemistry forward? We suggest some strategies and options to both increase the use of green chemistry principles and to also increase stakeholders' understanding of the importance and utility of green chemistry in their daily lives. For example, our main suggestions are that an inclusive, multidisciplinary network would aid in coordinating data and in translating the science into user friendly tools, and that an educational component embedded in this greater effort would also serve to move green chemistry forward.

Chemistry for the nuclear energy of the future

International Nuclear Information System (INIS)

Chmielewski, A.G.

2011-01-01

Chemistry - radiochemistry, radiation chemistry and nuclear chemical engineering play a very important role in the nuclear power development. Even at present, the offered technology is well developed, but still several improvements are needed and proposed. These developments concern all stages of the technology; front end, reactor operation (coolant chemistry and installation components decontamination, noble gas release control), back end of fuel cycle, etc. Chemistry for a partitioning and a transmutation is a new challenge for the chemists and chemical engineers. The IV th generation of nuclear reactors cannot be developed without chemical solutions for fuel fabrication, radiation-coolants interaction phenomena understanding and spent fuel/waste treatment technologies elaboration. Radiochemical analytical methods are fundamental for radioecological monitoring of radioisotopes of natural and anthropological origin. This paper addresses just a few subjects and is not a detailed overview of the field, however it illustrates a role of chemistry for a safe and economical nuclear power development. (author)

Elementary and brief introduction of hadronic chemistry

Science.gov (United States)

Tangde, Vijay M.

2013-10-01

The discipline, today known as Quantum Chemistry for atomic and subatomic level interactions has no doubt made a significant historical contributions to the society. Despite of its significant achievements, quantum chemistry is also known for its widespread denial of insufficiencies it inherits. An Italian-American Scientist Professor Ruggero Maria Santilli during his more than five decades of dedicated and sustained research has denounced the fact that quantum chemistry is mostly based on mere nomenclatures without any quantitative scientific contents. Professor R M Santilli first formulated the iso-, geno- and hyper-mathematics [1-4] that helped in understanding numerous diversified problems and removing inadequacies in most of the established and celebrated theories of 20th century physics and chemistry. This involves the isotopic, genotopic, etc. lifting of Lie algebra that generated Lie admissible mathematics to properly describe irreversible processes. The studies on Hadronic Mechanics in general and chemistry in particular based on Santilli's mathematics[3-5] for the first time has removed the very fundamental limitations of quantum chemistry [2, 6-8]. In the present discussion, we have briefly reviewed the conceptual foundations of Hadronic Chemistry that imparts the completeness to the Quantum Chemistry via an addition of effects at distances of the order of 1 fm (only) which are assumed to be Non-linear, Non-local, Non-potential, Non-hamiltonian and thus Non-unitary and its application in development of a new chemical species called Magnecules.

Theoretical chemistry periodicities in chemistry and biology

CERN Document Server

Eyring, Henry

1978-01-01

Theoretical Chemistry: Periodicities in Chemistry and Biology, Volume 4 covers the aspects of theoretical chemistry. The book discusses the stably rotating patterns of reaction and diffusion; the chemistry of inorganic systems exhibiting nonmonotonic behavior; and population cycles. The text also describes the mathematical modeling of excitable media in neurobiology and chemistry; oscillating enzyme reactions; and oscillatory properties and excitability of the heart cell membrane. Selected topics from the theory of physico-chemical instabilities are also encompassed. Chemists, mechanical engin

Using chemistry and microfluidics to understand the spatial dynamics of complex biological networks.

Science.gov (United States)

Kastrup, Christian J; Runyon, Matthew K; Lucchetta, Elena M; Price, Jessica M; Ismagilov, Rustem F

2008-04-01

Understanding the spatial dynamics of biochemical networks is both fundamentally important for understanding life at the systems level and also has practical implications for medicine, engineering, biology, and chemistry. Studies at the level of individual reactions provide essential information about the function, interactions, and localization of individual molecular species and reactions in a network. However, analyzing the spatial dynamics of complex biochemical networks at this level is difficult. Biochemical networks are nonequilibrium systems containing dozens to hundreds of reactions with nonlinear and time-dependent interactions, and these interactions are influenced by diffusion, flow, and the relative values of state-dependent kinetic parameters. To achieve an overall understanding of the spatial dynamics of a network and the global mechanisms that drive its function, networks must be analyzed as a whole, where all of the components and influential parameters of a network are simultaneously considered. Here, we describe chemical concepts and microfluidic tools developed for network-level investigations of the spatial dynamics of these networks. Modular approaches can be used to simplify these networks by separating them into modules, and simple experimental or computational models can be created by replacing each module with a single reaction. Microfluidics can be used to implement these models as well as to analyze and perturb the complex network itself with spatial control on the micrometer scale. We also describe the application of these network-level approaches to elucidate the mechanisms governing the spatial dynamics of two networkshemostasis (blood clotting) and early patterning of the Drosophila embryo. To investigate the dynamics of the complex network of hemostasis, we simplified the network by using a modular mechanism and created a chemical model based on this mechanism by using microfluidics. Then, we used the mechanism and the model to

Concept-Oriented Task Design: Making Purposeful Case Comparisons in Organic Chemistry

Science.gov (United States)

Graulich, Nicole; Schween, Michael

2018-01-01

Acquiring conceptual understanding seems to be one of the main challenges students face when studying organic chemistry. Traditionally, organic chemistry presents an extensive variety of chemical transformations, which often lead students to recall an organic transformation rather than apply conceptual knowledge. Strong surface level focus and…

BWR and PWR chemistry operating experience and perspectives

International Nuclear Information System (INIS)

Fruzzetti, K.; Garcia, S.; Lynch, N.; Reid, R.

2014-01-01

It is well recognized that proper control of water chemistry plays a critical role in ensuring the safe and reliable operation of Boiling Water Reactors (BWRs) and Pressurized Water Reactors (PWRs). State-of-the-art water chemistry programs reduce general and localized corrosion of reactor coolant system, steam cycle equipment, and fuel cladding materials; ensure continued integrity of cycle components; and reduce radiation fields. Once a particular nuclear plant component has been installed or plant system constructed, proper water chemistry provides a global tool to mitigate materials degradation problems, thereby reducing the need for costly repairs or replacements. Recognizing the importance of proper chemistry control and the value in understanding the relationship between chemistry guidance and actual operating experience, EPRI continues to collect, monitor, and evaluate operating data from BWRs and PWRs around the world. More than 900 cycles of valuable BWR and PWR operating chemistry data has been collected, including online, startup and shutdown chemistry data over more than 10 years (> 20 years for BWRs). This paper will provide an overview of current trends in BWR and PWR chemistry, focusing on plants in the U.S.. Important chemistry parameters will be highlighted and discussed in the context of the EPRI Water Chemistry Guidelines requirements (i.e., those parameters considered to be of key importance as related to the major goals identified in the EPRI Guidelines: materials integrity; fuel integrity; and minimizing plant radiation fields). Perspectives will be provided in light of recent industry initiatives and changes in the EPRI BWR and PWR Water Chemistry Guidelines. (author)

A Framework for Understanding Student Nurses' Experience of Chemistry as Part of a Health Science Course

Science.gov (United States)

Boddey, Kerrie; de Berg, Kevin

2018-01-01

Twenty-seven first-year nursing students, divided across six focus groups formed on the basis of their past chemistry experience, were interviewed about their chemistry experience as a component of a Health Science unit. Information related to learning and academic performance was able to be established from student conversations resulting in…

Optimizing the continuum of cycle chemistry

Energy Technology Data Exchange (ETDEWEB)

Mathews, James A. [Electric Power Research Institute, Charlotte, NC (United States). Generation Sector, Steam and Cycle Chemistry

2012-07-15

In 2011 EPRI issued the fourth (4th) major revision to the cycle chemistry guidelines for fossil plants, re-combining the previously segregated ''treatment'' guidelines into a comprehensive document. As with each of the series of previous revisions, the 2011 updated guidelines focus on the optimization of chemistry practices for maintaining the availability, reliability, and economic performance of fossil power plants. A key element in the development and revision of the guidelines is extensive research conducted over the past fifty (50) plus years. Providing an understanding the elements of the power plant cycle and the interrelationships of the best chemistry practices are a basic tenet of the introductory chapters of the guidelines. The target values for each treatment practice and location in the cycle are discussed with specific emphasis on optimization and customization to achieve excellent corrosion protection and elimination of deposition and component damage and failure. The rationale for proper chemistry is presented; for example properly maintaining oxidizing potentials, impact of temperature on pH control, assuring alkaline (sodium) neutralization for controlling boiler corrosion, and other considerations. (orig.)

Scaling properties of conduction velocity in heterogeneous excitable media

Science.gov (United States)

Shajahan, T. K.; Borek, Bartłomiej; Shrier, Alvin; Glass, Leon

2011-10-01

Waves of excitation through excitable media, such as cardiac tissue, can propagate as plane waves or break up to form reentrant spiral waves. In diseased hearts reentrant waves can be associated with fatal cardiac arrhythmias. In this paper we investigate the conditions that lead to wave break, reentry, and propagation failure in mathematical models of heterogeneous excitable media. Two types of heterogeneities are considered: sinks are regions in space in which the voltage is fixed at its rest value, and breaks are nonconducting regions with no-flux boundary conditions. We find that randomly distributed heterogeneities in the medium have a decremental effect on the velocity, and above a critical density of such heterogeneities the conduction fails. Using numerical and analytical methods we derive the general relationship among the conduction velocity, density of heterogeneities, diffusion coefficient, and the rise time of the excitation in both two and three dimensions. This work helps us understand the factors leading to reduced propagation velocity and the formation of spiral waves in heterogeneous excitable media.

Creating the Chemistry in Cellular Respiration Concept Inventory (CCRCI)

Science.gov (United States)

Forshee, Jay Lance, II

Students at our institution report cellular respiration to be the most difficult concept they encounter in undergraduate biology, but why students find this difficult is unknown. Students may find cellular respiration difficult because there is a large amount of steps, or because there are persistent, long-lasting misconceptions and misunderstandings surrounding their knowledge of chemistry, which affect their performance on cellular respiration assessments. Most studies of cellular respiration focus on student macro understanding of the process related to breathing, and matter and energy. To date, no studies identify which chemistry concepts are most relevant to students' development of an understanding of the process of cellular respiration or have developed an assessment to measure student understanding of them. Following the Delphi method, the researchers conducted expert interviews with faculty members from four-year, masters-, and PhD-granting institutions who teach undergraduate general biology, and are experts in their respective fields of biology. From these interviews, researchers identified twelve chemistry concepts important to understanding cellular respiration and using surveys, these twelve concepts were refined into five (electron transfer, energy transfer, thermodynamics (law/conservation), chemical reactions, and gradients). The researchers then interviewed undergraduate introductory biology students at a large Midwestern university to identify their knowledge and misconceptions of the chemistry concepts that the faculty had identified previously as important. The CCRCI was developed using the five important chemistry concepts underlying cellular respiration. The final version of the CCRCI was administered to n=160 introductory biology students during the spring 2017 semester. Reliability of the CCRCI was evaluated using Cronbach's alpha (=.7) and split-half reliability (=.769), and validity of the instrument was assessed through content validity

Water chemistry and behavior of materials in PWRs and BWRs

Energy Technology Data Exchange (ETDEWEB)

Aaltonen, P; Hanninen, H [VTT Manufacturing Technology, Espoo (Finland)

1997-09-01

Water chemistry plays a major role in corrosion and in activity transport in NPP`s. Although a full understanding of all mechanisms involved in corrosion does not exist, controlling of the water chemistry has achieved good results in recent years. Water chemistry impacts upon the operational safety of LWR`s in two main ways: integrity of pressure boundary materials and, activity transport and out-of-core radiation fields. This paper will describe application of water chemistry control in operating reactors to prevent corrosion. Some problems experienced in LWR`s will be reviewed for the design of the nuclear heating reactors (NHR). (author). 18 refs, 10 figs, 5 tabs.

Water chemistry and behavior of materials in PWRs and BWRs

International Nuclear Information System (INIS)

Aaltonen, P.; Hanninen, H.

1997-01-01

Water chemistry plays a major role in corrosion and in activity transport in NPP's. Although a full understanding of all mechanisms involved in corrosion does not exist, controlling of the water chemistry has achieved good results in recent years. Water chemistry impacts upon the operational safety of LWR's in two main ways: integrity of pressure boundary materials and, activity transport and out-of-core radiation fields. This paper will describe application of water chemistry control in operating reactors to prevent corrosion. Some problems experienced in LWR's will be reviewed for the design of the nuclear heating reactors (NHR). (author). 18 refs, 10 figs, 5 tabs

Coupled petrological-geodynamical modeling of a compositionally heterogeneous mantle plume

Science.gov (United States)

Rummel, Lisa; Kaus, Boris J. P.; White, Richard W.; Mertz, Dieter F.; Yang, Jianfeng; Baumann, Tobias S.

2018-01-01

Self-consistent geodynamic modeling that includes melting is challenging as the chemistry of the source rocks continuously changes as a result of melt extraction. Here, we describe a new method to study the interaction between physical and chemical processes in an uprising heterogeneous mantle plume by combining a geodynamic code with a thermodynamic modeling approach for magma generation and evolution. We pre-computed hundreds of phase diagrams, each of them for a different chemical system. After melt is extracted, the phase diagram with the closest bulk rock chemistry to the depleted source rock is updated locally. The petrological evolution of rocks is tracked via evolving chemical compositions of source rocks and extracted melts using twelve oxide compositional parameters. As a result, a wide variety of newly generated magmatic rocks can in principle be produced from mantle rocks with different degrees of depletion. The results show that a variable geothermal gradient, the amount of extracted melt and plume excess temperature affect the magma production and chemistry by influencing decompression melting and the depletion of rocks. Decompression melting is facilitated by a shallower lithosphere-asthenosphere boundary and an increase in the amount of extracted magma is induced by a lower critical melt fraction for melt extraction and/or higher plume temperatures. Increasing critical melt fractions activates the extraction of melts triggered by decompression at a later stage and slows down the depletion process from the metasomatized mantle. Melt compositional trends are used to determine melting related processes by focusing on K2O/Na2O ratio as indicator for the rock type that has been molten. Thus, a step-like-profile in K2O/Na2O might be explained by a transition between melting metasomatized and pyrolitic mantle components reproducible through numerical modeling of a heterogeneous asthenospheric mantle source. A potential application of the developed method

The tip of the iceberg in organic chemistry classes : how do students deal with the invisible?

OpenAIRE

Graulich, Nicole

2015-01-01

Organic chemistry education is one of the youngest research areas among all chemistry related research efforts, and its published scholarly work has become vibrant and diverse over the last 15 years. Research on problem-solving behavior, students´ use of the arrow-pushing formalism, the investigation of students´ conceptual knowledge and their cognitive skills have shaped our understanding of college students´ understanding in organic chemistry classes. This review provides an overview of res...

Laboratory Investigations of Stratospheric Halogen Chemistry

Science.gov (United States)

Wine, Paul H.; Nicovich, J. Michael; Stickel, Robert E.; Hynes, Anthony J.

1997-01-01

A final report for the NASA-supported project on laboratory investigations of stratospheric halogen chemistry is presented. In recent years, this project has focused on three areas of research: (1) kinetic, mechanistic, and thermochemical studies of reactions which produce weakly bound chemical species of atmospheric interest; (2) development of flash photolysis schemes for studying radical-radical reactions of stratospheric interest; and (3) photochemistry studies of interest for understanding stratospheric chemistry. The first section of this paper contains a discussion of work which has not yet been published. All subsequent chapters contain reprints of published papers that acknowledge support from this grant.

Site-specific antibody-drug conjugates: the nexus of bioorthogonal chemistry, protein engineering, and drug development.

Science.gov (United States)

Agarwal, Paresh; Bertozzi, Carolyn R

2015-02-18

Antibody-drug conjugates (ADCs) combine the specificity of antibodies with the potency of small molecules to create targeted drugs. Despite the simplicity of this concept, generation of clinically successful ADCs has been very difficult. Over the past several decades, scientists have learned a great deal about the constraints on antibodies, linkers, and drugs as they relate to successful construction of ADCs. Once these components are in hand, most ADCs are prepared by nonspecific modification of antibody lysine or cysteine residues with drug-linker reagents, which results in heterogeneous product mixtures that cannot be further purified. With advances in the fields of bioorthogonal chemistry and protein engineering, there is growing interest in producing ADCs by site-specific conjugation to the antibody, yielding more homogeneous products that have demonstrated benefits over their heterogeneous counterparts in vivo. Here, we chronicle the development of a multitude of site-specific conjugation strategies for assembly of ADCs and provide a comprehensive account of key advances and their roots in the fields of bioorthogonal chemistry and protein engineering.

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

Science.gov (United States)

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…

Chemistry Students' Challenges in Using MBL's in Science Laboratories.

Science.gov (United States)

Atar, Hakan Yavuz

Understanding students' challenges about using microcomputer based laboratories (MBLs) would provide important data in understanding the appropriateness of using MBLs in high school chemistry laboratories. Identifying students' concerns about this technology will in part help educators identify the obstacles to science learning when using this…

Coordinated Energy Management in Heterogeneous Processors

Directory of Open Access Journals (Sweden)

Indrani Paul

2014-01-01

Full Text Available This paper examines energy management in a heterogeneous processor consisting of an integrated CPU–GPU for high-performance computing (HPC applications. Energy management for HPC applications is challenged by their uncompromising performance requirements and complicated by the need for coordinating energy management across distinct core types – a new and less understood problem. We examine the intra-node CPU–GPU frequency sensitivity of HPC applications on tightly coupled CPU–GPU architectures as the first step in understanding power and performance optimization for a heterogeneous multi-node HPC system. The insights from this analysis form the basis of a coordinated energy management scheme, called DynaCo, for integrated CPU–GPU architectures. We implement DynaCo on a modern heterogeneous processor and compare its performance to a state-of-the-art power- and performance-management algorithm. DynaCo improves measured average energy-delay squared (ED2 product by up to 30% with less than 2% average performance loss across several exascale and other HPC workloads.

A Supramolecular Approach to Medicinal Chemistry: Medicine Beyond the Molecule

Science.gov (United States)

Smith, David K.

2005-03-01

This article focuses on the essential roles played by intermolecular forces in mediating the interactions between chemical molecules and biological systems. Intermolecular forces constitute a key topic in chemistry programs, yet can sometimes seem disconnected from real-life applications. However, by taking a "supramolecular" view of medicinal chemistry and focusing on interactions between molecules, it is possible to come to a deeper understanding of recent developments in medicine. This allows us to gain a real insight into the interface between biology and chemistry—an interdisciplinary area that is crucial for the development of modern medicinal products. This article emphasizes a conceptual view of medicinal chemistry, which has important implications for the future, as the supramolecular approach to medicinal-chemistry products outlined here is rapidly allowing nanotechnology to converge with medicine. In particular, this article discusses recent developments including the rational design of drugs such as Relenza and Tamiflu, the mode of action of vancomycin, and the mechanism by which bacteria develop resistance, drug delivery using cyclodextrins, and the importance of supramolecular chemistry in understanding protein aggregation diseases such as Alzheimer's and Creutzfield Jacob. The article also indicates how taking a supramolecular approach will enable the development of new nanoscale medicines.

Medicinal chemistry for 2020

Science.gov (United States)

Satyanarayanajois, Seetharama D; Hill, Ronald A

2011-01-01

Rapid advances in our collective understanding of biomolecular structure and, in concert, of biochemical systems, coupled with developments in computational methods, have massively impacted the field of medicinal chemistry over the past two decades, with even greater changes appearing on the horizon. In this perspective, we endeavor to profile some of the most prominent determinants of change and speculate as to further evolution that may consequently occur during the next decade. The five main angles to be addressed are: protein–protein interactions; peptides and peptidomimetics; molecular diversity and pharmacological space; molecular pharmacodynamics (significance, potential and challenges); and early-stage clinical efficacy and safety. We then consider, in light of these, the future of medicinal chemistry and the educational preparation that will be required for future medicinal chemists. PMID:22004084

Chemistry in protoplanetary disks

Science.gov (United States)

Semenov, D. A.

2012-01-01

In this lecture I discuss recent progress in the understanding of the chemical evolution of protoplanetary disks that resemble our Solar system during the first ten million years. At the verge of planet formation, strong variations of temperature, density, and radiation intensities in these disks lead to a layered chemical structure. In hot, dilute and heavily irradiated atmosphere only simple radicals, atoms, and atomic ions can survive, formed and destroyed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex (organic) species are synthesized.

(Chemistry of the global atmosphere)

Energy Technology Data Exchange (ETDEWEB)

Marland, G.

1990-09-27

The traveler attended the conference The Chemistry of the Global Atmosphere,'' and presented a paper on the anthropogenic emission of carbon dioxide (CO{sub 2}) to the atmosphere. The conference included meetings of the International Global Atmospheric Chemistry (IGAC) programme, a core project of the International Geosphere/Biosphere Programme (IGBP) and the traveler participated in meetings on the IGAC project Development of Global Emissions Inventories'' and agreed to coordinate the working group on CO{sub 2}. Papers presented at the conference focused on the latest developments in analytical methods, modeling and understanding of atmospheric CO{sub 2}, CO, CH{sub 4}, N{sub 2}O, SO{sub 2}, NO{sub x}, NMHCs, CFCs, and aerosols.

Complex chemistry

International Nuclear Information System (INIS)

Kim, Bong Gon; Kim, Jae Sang; Kim, Jin Eun; Lee, Boo Yeon

2006-06-01

This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

Radiation chemistry in solvent extraction: FY2010 Research

Energy Technology Data Exchange (ETDEWEB)

Bruce J. Mincher; Leigh R. Martin; Stephen P. Mezyk

2010-09-01

This report summarizes work accomplished under the Fuel Cycle Research and Development (FCR&D) program in the area of radiation chemistry during FY 2010. The tasks assigned during FY 2010 included: • Development of techniques to measure free radical reaction kinetics in the organic phase. • Initiation of an alpha-radiolysis program • Initiation of an effort to understand dose rate effects in radiation chemistry • Continued work to characterize TALSPEAK radiation chemistry Progress made on each of these tasks is reported here. Briefly, a method was developed and used to measure the kinetics of the reactions of the •NO3 radical with solvent extraction ligands in organic solution, and the method to measure •OH radical reactions under the same conditions has been designed. Rate constants for the CMPO and DMDOHEMA reaction with •NO3 radical in organic solution are reported. Alpha-radiolysis was initiated on samples of DMDOHEMA in alkane solution using He ion beam irradiation and 211At isotope irradiation. The samples are currently being analyzed for comparison to DMDOHEMA ?-irradiations using a custom-developed mass spectrometric method. Results are also reported for the radiolytic generation of nitrous acid, in ?-irradiated nitric acid. It is shown that the yield of nitrous acid is unaffected by an order-of-magnitude change in dose rate. Finally, recent results for TALSPEAK radiolysis are reported, summarizing the effects on solvent extraction efficiency due to HDEHP irradiation, and the stable products of lactic acid and DTPA irradiation. In addition, results representing increased scope are presented for the radiation chemistry program. These include an investigation of the effect of metal complexation on radical reaction kinetics using DTPA as an example, and the production of a manuscript reporting the mechanism of Cs-7SB radiolysis. The Cs-7SB work takes advantage of recent results from a current LDRD program to understand the fundamental chemistry

State-of-the-art in Heterogeneous Computing

Directory of Open Access Journals (Sweden)

Andre R. Brodtkorb

2010-01-01

Full Text Available Node level heterogeneous architectures have become attractive during the last decade for several reasons: compared to traditional symmetric CPUs, they offer high peak performance and are energy and/or cost efficient. With the increase of fine-grained parallelism in high-performance computing, as well as the introduction of parallelism in workstations, there is an acute need for a good overview and understanding of these architectures. We give an overview of the state-of-the-art in heterogeneous computing, focusing on three commonly found architectures: the Cell Broadband Engine Architecture, graphics processing units (GPUs, and field programmable gate arrays (FPGAs. We present a review of hardware, available software tools, and an overview of state-of-the-art techniques and algorithms. Furthermore, we present a qualitative and quantitative comparison of the architectures, and give our view on the future of heterogeneous computing.

Well-defined silica-supported zirconium–imido complexes mediated heterogeneous imine metathesis

KAUST Repository

Hamzaoui, Bilel

2016-02-15

Upon prolonged thermal exposure under vacuum, a well-defined single-site surface species [(≡Si-O-)Zr(NEt2)3] (1) evolves into an ethylimido complex [(≡Si-O-)Zr(=NEt)NEt2] (2). Reactions of 2 with an imine substrate result in imido/imine (=NRi, R: Et, Ph) exchange (metathesis) with the formation of [(≡Si-O-)Zr(=NPh)NEt2] (3). Compounds 2 and 3 effectively catalyze imine/imine cross-metathesis and are thus considered as the first heterogeneous catalysts active for imine metathesis. © The Royal Society of Chemistry 2016.

Well-defined silica-supported zirconium–imido complexes mediated heterogeneous imine metathesis

KAUST Repository

Hamzaoui, Bilel; Pelletier, Jeremie; Abou-Hamad, Edy; Basset, Jean-Marie

2016-01-01

Upon prolonged thermal exposure under vacuum, a well-defined single-site surface species [(≡Si-O-)Zr(NEt2)3] (1) evolves into an ethylimido complex [(≡Si-O-)Zr(=NEt)NEt2] (2). Reactions of 2 with an imine substrate result in imido/imine (=NRi, R: Et, Ph) exchange (metathesis) with the formation of [(≡Si-O-)Zr(=NPh)NEt2] (3). Compounds 2 and 3 effectively catalyze imine/imine cross-metathesis and are thus considered as the first heterogeneous catalysts active for imine metathesis. © The Royal Society of Chemistry 2016.

Diverse applications of radiation chemistry

International Nuclear Information System (INIS)

Cooper, R.

1998-01-01

Radiation chemistry began as early radiotherapists needed a reliable and appropriate dosimeter. The iron sulphate dosimeter, using ferrous iron in sulphuric acid and oxidation by irradiation, was a nasty brew of chemicals but it was sensitive, reliable and conveniently had the same density as human tissue. Water irradiation chemistry studies were driven by the need to understand the fundamental processes in radiotherapy; to control the corrosion problems in the cooling/ heat exchange systems of nuclear reactors and to find stable solvents and reagents for use in spent fuel element processing. The electrical and mechanical stability of materials in high radiation fields stimulated the attention of radiation chemists to the study of defects in solids. The coupled use of radiation and Electron Spin Resonance (ESR) enabled the identity of defect structures to be probed. This research led to the development of the sensitive Thermoluminescent Dosimeters, TLD's and a technique for dating of archaeological pottery artefacts. Radiation chemistry in the area of medicine is very active with fundamental studies of the mechanism of DNA strand breakage and the development of radiation sensitisers and protectors for therapeutic purposes. The major area of polymer radiation chemistry is one which Australia commands great international respect

Dynamic heterogeneity and life history variability in the kittiwake

DEFF Research Database (Denmark)

Steiner, Uli; Tuljapurkar, Shripad; Orzack, Steven Hecht

2010-01-01

1. Understanding the evolution of life histories requires an assessment of the process that generates variation in life histories. Within-population heterogeneity of life histories can be dynamically generated by stochastic variation of reproduction and survival or be generated by individual...... differences that are fixed at birth. 2. We show for the kittiwake that dynamic heterogeneity is a sufficient explanation of observed variation of life histories. 3. The total heterogeneity in life histories has a small contribution from reproductive stage dynamics and a large contribution from survival...... differences. We quantify the diversity in life histories by metrics computed from the generating stochastic process. 4. We show how dynamic heterogeneity can be used as a null model and also how it can lead to positive associations between reproduction and survival across the life span. 5. We believe our...

Teaching and learning distillation in chemistry laboratory courses

Science.gov (United States)

van Keulen, Hanno; Mulder, Theo H. M.; Goedhart, Martin J.; Verdonk, Adri H.

This study investigates the problems chemistry majors have with learning distillation in traditional chemistry laboratory courses. Using an interpretive cyclic research design, we collected and interpreted data, mainly in the form of observation notes and transcriptions of the discourse that takes place during laboratory courses. It was found that students experience numerous problems; these are described and interpreted. We summarize students' problems in four categories: (a) students use an independent component conception; (b) they have insufficient understanding of the properties of vapor; (c) they regard distillation from a physical point of view; and (d) they do not have a practical understanding of thermodynamics. The main origin of these problems was found to lie with the traditional curriculum structure. Lecture courses and textbooks treat distillation in a generalized and decontextualized way, whereas decisions in actual distillations are always based on contextual features. It was found that textbooks and teachers often do not discriminate carefully and explicitly among five different contexts for distillation: organic synthesis, chemical analysis, analytical chemistry, physical chemistry, and preparation of products. Students take the generalized concepts at face value and apply them to all distillations regardless of context. They cannot interpret their observations or make reasoned decisions based on the theoretical framework of a specific context.Received: 2 May 1994; Revised: 14 December 1994;

Heterogeneous structure and its effect on properties and electrochemical behavior of ion-exchange membrane

Science.gov (United States)

Ariono, D.; Khoiruddin; Subagjo; Wenten, I. G.

2017-02-01

Generally, commercially available ion-exchange membrane (IEM) can be classified into homogeneous and heterogeneous membranes. The classification is based on degree of heterogeneity in membrane structure. It is well known that the heterogeneity greatly affects the properties of IEM, such as conductivity, permselectivity, chemical and mechanical stability. The heterogeneity also influences ionic and electrical current transfer behavior of IEM-based processes during their operation. Therefore, understanding the role of heterogeneity in IEM properties is important to provide preliminary information on their operability and applicability. In this paper, the heterogeneity and its effect on IEM properties are reviewed. Some models for describing the heterogeneity of IEM and methods for characterizing the degree of heterogeneity are discussed. In addition, the influence of heterogeneity on the performance of IEM-based processes and their electrochemical behavior are described.

Probing the Question Order Effect While Developing a Chemistry Concept Inventory

Science.gov (United States)

Undersander, Molly A.; Lund, Travis J.; Langdon, Laurie S.; Stains, Marilyne

2017-01-01

The design of assessment tools is critical to accurately evaluate students' understanding of chemistry. Although extensive research has been conducted on various aspects of assessment tool design, few studies in chemistry have focused on the impact of the order in which questions are presented to students on the measurement of students'…

Past, Present and Future of General Chemistry in the PUC-Rio.

Science.gov (United States)

Farias, Percio A. M.; Goulart, Mauricio S.; de Mello, Paulo Correa

This manuscript describes the role of chemistry as a vehicle for understanding many other basic sciences and engineering based on the experience acquired in the General Chemistry course at the "Center Technical-Scientific" at the Pontific Catholic University of Rio de Janeiro (CTC-PUC-Rio). A description of the history of the General…

General chemistry courses that can affect achievement: An action research study in developing a plan to improve undergraduate chemistry courses

Science.gov (United States)

Shweikeh, Eman

Over the past 50 years, considerable research has been dedicated to chemistry education. In evaluating principal chemistry courses in higher education, educators have noted the learning process for first-year general chemistry courses may be challenging. The current study investigated perceptions of faculty, students and administrators on chemistry education at three institutions in Southern California. Via action research, the study sought to develop a plan to improve student engagement in general chemistry courses. A mixed method was utilized to analyze different perceptions on key factors determining the level of commitment and engagement in general chemistry education. The approach to chemistry learning from both a faculty and student perspective was examined including good practices, experiences and extent of active participation. The research study considered well-known measures of effective education with an emphasis on two key components: educational practices and student behavior. Institutional culture was inclusively assessed where cognitive expectations of chemistry teaching and learning were communicated. First, the extent in which faculty members are utilizing the "Seven Principles for Good Practice in Undergraduate Education" in their instruction was explored. Second, student attitudes and approaches toward chemistry learning were examined. The focus was on investigating student understanding of the learning process and the structure of chemistry knowledge. The seven categories used to measure students' expectations for learning chemistry were: effort, concepts, math link, reality link, outcome, laboratory, and visualization. This analysis represents the views of 16 faculty and 140 students. The results validated the assertion that students need some competencies and skills to tackle the challenges of the chemistry learning process to deeply engage in learning. A mismatch exists between the expectations of students and those of the faculty

Understanding Ocean Acidification

Science.gov (United States)

National Oceanic and Atmospheric Administration, 2011

2011-01-01

This curriculum module is designed for students who are taking high school chemistry. Students should already have some experience with the following: (1) Understanding and reading the pH scale; (2) Knowledge of the carbon cycle; (3) Using scientific notation to express large and small values; and (4) Reading chemical equations. This curriculum…

Spatial Heterogeneity of the Forest Canopy Scales with the Heterogeneity of an Understory Shrub Based on Fractal Analysis

Directory of Open Access Journals (Sweden)

Catherine K. Denny

2017-04-01

Full Text Available Spatial heterogeneity of vegetation is an important landscape characteristic, but is difficult to assess due to scale-dependence. Here we examine how spatial patterns in the forest canopy affect those of understory plants, using the shrub Canada buffaloberry (Shepherdia canadensis (L. Nutt. as a focal species. Evergreen and deciduous forest canopy and buffaloberry shrub presence were measured with line-intercept sampling along ten 2-km transects in the Rocky Mountain foothills of west-central Alberta, Canada. Relationships between overstory canopy and understory buffaloberry presence were assessed for scales ranging from 2 m to 502 m. Fractal dimensions of both canopy and buffaloberry were estimated and then related using box-counting methods to evaluate spatial heterogeneity based on patch distribution and abundance. Effects of canopy presence on buffaloberry were scale-dependent, with shrub presence negatively related to evergreen canopy cover and positively related to deciduous cover. The effect of evergreen canopy was significant at a local scale between 2 m and 42 m, while that of deciduous canopy was significant at a meso-scale between 150 m and 358 m. Fractal analysis indicated that buffaloberry heterogeneity positively scaled with evergreen canopy heterogeneity, but was unrelated to that of deciduous canopy. This study demonstrates that evergreen canopy cover is a determinant of buffaloberry heterogeneity, highlighting the importance of spatial scale and canopy composition in understanding canopy-understory relationships.

Long-term flow/chemistry feedback in a porous medium with heterogenous permeability: Kinetic control of dissolution and precipitation

International Nuclear Information System (INIS)

Bolton, E.W.; Lasaga, A.C.; Rye, D.M.

1999-01-01

The kinetics of dissolution and precipitation is of central importance to understanding the long-term evolution of fluid flows in crustal environments, with implications for problems as diverse as nuclear waste disposal and crustal evolution. The authors examine the dynamics of such evolution for several geologically relevant permeability distributions (models for en-echelon cracks, an isolated sloping fractured zone, and two sloping high-permeability zones that are close enough together to interact). Although the focus is on a simple quartz matrix system, generic features emerge from this study that can aid in the broader goal of understanding the long-term feedback between flow and chemistry, where dissolution and precipitation is under kinetic control. Examples of thermal convection in a porous medium with spatially variable permeability reveal features of central importance to water-rock interaction. After a transient phase, an accelerated rate of change of porosity may be used with care to decrease computational time, as an alternative to the quasi-stationary state approximation (Lichtner, 1988). Kinetic effects produce features not expected by traditional assumptions made on the basis of equilibrium, for example, that cooling fluids are oversaturated and heating fluids are undersaturated with respect to silicic acid equilibrium. Indeed, the authors observe regions of downwelling oversaturated fluid experiencing heating and regions of upwelling, yet cooling, undersaturated fluid. When oscillatory convection is present, the amplitudes of oscillation generally increase with time in near-surface environments, whereas amplitudes tend to decrease over long times near the heated lower boundary. The authors examine the scaling behavior of characteristic length scales, of terms in the solute equation, and of the typical deviation from equilibrium, each as a function of the kinetic rate parameters

Whither Constructivism?--A Chemistry Teachers' Perspective

Science.gov (United States)

Niaz, Mansoor

2008-01-01

Constructivism in science education has been the subject of considerable debate in the science education literature. The purpose of this study was to facilitate chemistry teachers' understanding that the tentative nature of scientific knowledge leads to the coexistence and rivalries among different forms of constructivism in science education. The…

Pre-university Chemistry Students in a Mimicked Scholarly Peer Review

NARCIS (Netherlands)

van Rens, L.; Hermarij, P.; Pilot, A.; Beishuizen, J.J.; Hofman, H.; van der Wal, M.

2014-01-01

Peer review is a significant component in scientific research. Introducing peer review into inquiry processes may be regarded as an aim to develop student understanding regarding quality in inquiries. This study examines student understanding in inquiry peer reviews among pre-university chemistry

Measuring Heterogeneous Reaction Rates with ATR-FTIR Spectroscopy to Evaluate Chemical Fates in an Atmospheric Environment: A Physical Chemistry and Environmental Chemistry Laboratory Experiment

Science.gov (United States)

Roberts, Jason E.; Zeng, Guang; Maron, Marta K.; Mach, Mindy; Dwebi, Iman; Liu, Yong

2016-01-01

This paper reports an undergraduate laboratory experiment to measure heterogeneous liquid/gas reaction kinetics (ozone-oleic acid and ozone-phenothrin) using a flow reactor coupled to an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometer. The experiment is specially designed for an upper-level undergraduate Physical…

Illustrating Concepts in Physical Organic Chemistry with 3D Printed Orbitals

Science.gov (United States)

Robertson, Michael J.; Jorgensen, William L.

2015-01-01

Orbital theory provides a powerful tool for rationalizing and understanding many phenomena in chemistry. In most introductory chemistry courses, students are introduced to atomic and molecular orbitals in the form of two-dimensional drawings. In this work, we describe a general method for producing 3D printing files of orbital models that can be…

Macroeconomic Policies and Agent Heterogeneity

OpenAIRE

GOTTLIEB, Charles

2012-01-01

Defence date: 24 February 2012 Examining Board: Giancarlo Corsetti, Arpad Abraham, Juan Carlos Conesa, Jonathan Heathcote. This thesis contributes to the understanding of macroeconomic policies’ impact on the distribution of wealth. It belongs to the strand of literature that departs from the representative agent assumption and perceives agent heterogeneity and the induced disparities in wealth accumulation, as an important dimension of economic policy-making. Within such economic envir...

Astronomy Matters for Chemistry Teachers

Science.gov (United States)

Huebner, Jay S.; Vergenz, Robert A.; Smith, Terry L.

1996-11-01

The purpose of this paper is to encourage more chemistry teachers to become familiar with some of the basic ideas described in typical introductory astronomy courses (1 - 9), including those about the origin of elements and forms of matter. These ideas would enrich chemistry courses and help resolve some basic misconceptions that are expressed in many introductory texts (10 - 16) and journal articles for chemistry teachers (17, 18). These misconceptions are typified by statements such as "we can classify all substances as either elements or compounds," and "nature has provided 92 elements out of which all matter is composed." If students accept these misconceptions, they could be deprived of (i) an appreciation of the history of elements and knowing that the elemental composition of the universe continues to evolve, (ii) knowing that of the first 92 elements in the periodic table, technetium and promethium do not occur naturally on Earth, and (iii) understanding that there are forms of matter other than elements and compounds. This paper briefly explores these ideas.

Quasi-linear score for capturing heterogeneous structure in biomarkers.

Science.gov (United States)

Omae, Katsuhiro; Komori, Osamu; Eguchi, Shinto

2017-06-19

Linear scores are widely used to predict dichotomous outcomes in biomedical studies because of their learnability and understandability. Such approaches, however, cannot be used to elucidate biodiversity when there is heterogeneous structure in target population. Our study was focused on describing intrinsic heterogeneity in predictions. Because heterogeneity can be captured by a clustering method, integrating different information from different clusters should yield better predictions. Accordingly, we developed a quasi-linear score, which effectively combines the linear scores of clustered markers. We extended the linear score to the quasi-linear score by a generalized average form, the Kolmogorov-Nagumo average. We observed that two shrinkage methods worked well: ridge shrinkage for estimating the quasi-linear score, and lasso shrinkage for selecting markers within each cluster. Simulation studies and applications to real data show that the proposed method has good predictive performance compared with existing methods. Heterogeneous structure is captured by a clustering method. Quasi-linear scores combine such heterogeneity and have a better predictive ability compared with linear scores.

Modeling of meteorology, chemistry and aerosol for the 2017 Utah Winter Fine Particle Study

Science.gov (United States)

McKeen, S. A.; Angevine, W. M.; McDonald, B.; Ahmadov, R.; Franchin, A.; Middlebrook, A. M.; Fibiger, D. L.; McDuffie, E. E.; Womack, C.; Brown, S. S.; Moravek, A.; Murphy, J. G.; Trainer, M.

2017-12-01

The Utah Winter Fine Particle Study (UWFPS-17) field project took place during January and February of 2017 within the populated region of the Great Salt Lake, Utah. The study focused on understanding the meteorology and chemistry associated with high particulate matter (PM) levels often observed near Salt Lake City during stable wintertime conditions. Detailed composition and meteorological observations were taken from the NOAA Twin-Otter aircraft and several surface sites during the study period, and extremely high aerosol conditions were encountered for two cold-pool episodes occurring in the last 2 weeks of January. A clear understanding of the photochemical and aerosol processes leading to these high PM events is still lacking. Here we present high spatiotemporal resolution simulations of meteorology, PM and chemistry over Utah from January 13 to February 1, 2017 using the WRF/Chem photochemical model. Correctly characterizing the meteorology is difficult due to the complex terrain and shallow inversion layers. We discuss the approach and limitations of the simulated meteorology, and evaluate low-level pollutant mixing using vertical profiles from missed airport approaches by the NOAA Twin-Otter performed routinely during each flight. Full photochemical simulations are calculated using NOx, ammonia and VOC emissions from the U.S. EPA NEI-2011 emissions inventory. Comparisons of the observed vertical column amounts of NOx, ammonia, aerosol nitrate and ammonium with model results shows the inventory estimates for ammonia emissions are low by a factor of four and NOx emissions are low by nearly a factor of two. The partitioning of both nitrate and NH3 between gas and particle phase depends strongly on the NH3 and NOx emissions to the model and calculated NOx to nitrate conversion rates. These rates are underestimated by gas-phase chemistry alone, even though surface snow albedo increases photolysis rates by nearly a factor of two. Several additional conversion

Hot atom chemistry of monovalent atoms in organic condensed phases

International Nuclear Information System (INIS)

Stoecklin, G.

1975-01-01

The advantages and disadvantages of hot atom studies in condensed organic phases are considered, and recent advances in condensed phase organic hot atom chemistry of recoil tritium and halogen atoms are discussed. Details are presented of the present status and understanding of liquid phase hot atom chemistry and also that of organic solids. The consequences of the Auger effect in condensed organic systems are also considered. (author)

Population dynamics on heterogeneous bacterial substrates

Science.gov (United States)

Mobius, Wolfram; Murray, Andrew W.; Nelson, David R.

2012-02-01

How species invade new territories and how these range expansions influence the population's genotypes are important questions in the field of population genetics. The majority of work addressing these questions focuses on homogeneous environments. Much less is known about the population dynamics and population genetics when the environmental conditions are heterogeneous in space. To better understand range expansions in two-dimensional heterogeneous environments, we employ a system of bacteria and bacteriophage, the viruses of bacteria. Thereby, the bacteria constitute the environment in which a population of bacteriophages expands. The spread of phage constitutes itself in lysis of bacteria and thus formation of clear regions on bacterial lawns, called plaques. We study the population dynamics and genetics of the expanding page for various patterns of environments.

Review of the Scientific Understanding of Radioactive Waste at the U.S. DOE Hanford Site

Energy Technology Data Exchange (ETDEWEB)

Peterson, Reid A.; Buck, Edgar C.; Chun, Jaehun; Daniel, Richard C.; Herting, Daniel L. [Washington River Protection Solutions, Richland, Washington 99354, United States; Ilton, Eugene S.; Lumetta, Gregg J.; Clark, Sue B. [Chemistry

2018-01-02

This paper reviews the origin and chemical and rheological complexity of radioactive waste at the U.S. Department of Energy’s Hanford Site. The waste, stored in underground tanks, was generated via three distinct processes over decades of plutonium extraction operations. Although close records were kept of original waste disposition, tank-to-tank transfers and conditions that impede equilibrium complicate our understanding of the chemistry, phase composition, and rheology of the waste. Tank waste slurries comprise particles and aggregates from nano to micron scales, with varying densities, morphologies, heterogeneous compositions, and complicated responses to flow regimes and process conditions. Further, remnant or changing radiation fields may affect the stability and rheology of the waste. These conditions pose challenges for transport through conduits or pipes to treatment plants for vitrification. Additionally, recalcitrant boehmite degrades glass quality and must be reduced prior to vitrification, but dissolves much more slowly than predicted given surface normalized rates. Existing empirical models based on ex situ experiments and observations lack true predictive capabilities. Recent advances in in situ microscopy, aberration corrected TEM, theoretical modeling across scales, and experimental methods for probing the physics and chemistry at mineral-fluid and mineral-mineral interfaces are being implemented to build robustly predictive physics-based models.

Future Science Teachers' Understandings of Diffusion and Osmosis Concepts

Science.gov (United States)

Tomazic, Iztok; Vidic, Tatjana

2012-01-01

The concepts of diffusion and osmosis cross the disciplinary boundaries of physics, chemistry and biology. They are important for understanding how biological systems function. Since future (pre-service) science teachers in Slovenia encounter both concepts at physics, chemistry and biology courses during their studies, we assessed the first-,…

Observational constraints on interstellar chemistry

International Nuclear Information System (INIS)

Winnewisser, G.

1984-01-01

The author points out presently existing observational constraints in the detection of interstellar molecular species and the limits they may cast on our knowledge of interstellar chemistry. The constraints which arise from the molecular side are summarised and some technical difficulties encountered in detecting new species are discussed. Some implications for our understanding of molecular formation processes are considered. (Auth.)

Heterogeneous anion-selective membranes: Influence of a water-soluble component in the membrane on the morphology and ionic conductivity

Czech Academy of Sciences Publication Activity Database

Schauer, Jan; Hnát, J.; Brožová, Libuše; Žitka, Jan; Bouzek, K.

401/402, 15 May (2012), s. 83-88 ISSN 0376-7388 R&D Projects: GA MŠk(CZ) 7E08005 EU Projects: European Commission(XE) 212903 - WELTEMP Institutional research plan: CEZ:AV0Z40500505 Keywords : heterogeneous membrane * anion-exchange membrane * membrane morphology Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.093, year: 2012

Chemistry of nuclear resources, technology, and waste

International Nuclear Information System (INIS)

Keller, O.L. Jr.

1978-01-01

Chemistry is being called on today to obtain useful results in areas that have been found very difficult for it in the past, but new instrumentation and new theories are allowing much progress. The area of hydrolytic phenomena and colloid chemistry, as exemplified by the plutonium polymer problem, is clearly entering a new phase in which it can be studied in a much more controlled and understandable manner. The same is true of the little studied interfacial regions, where so much important chemistry occurs in solvent extraction and other systems. The studies of the adsorption phenomena on clays are an illustration of the new and useful modeling of geochemical phenomena that is now possible. And finally, the chemist is called upon to participate in the developement and evaluation of models for nuclear waste isolation requiring extrapolations of hundreds to hundreds of thousands of years into the future. It is shown that chemistry may be useful in keeping the extrapolations in the shorter time spans, and also in selecting the best materials for containment. 36 figures

Astronomical chemistry.

Science.gov (United States)

Klemperer, William

2011-01-01

The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic.

How Do Organic Chemistry Students Understand and Apply Hydrogen Bonding?

Science.gov (United States)

Henderleiter, J.; Smart, R.; Anderson, J.; Elian, O.

2001-08-01

Students completing a year-long organic chemistry sequence were interviewed to assess how they understood, explained, and applied knowledge of hydrogen bonding to the physical behavior of molecules. Students were asked to define hydrogen bonding and explain situations in which hydrogen bonding could occur. They were asked to predict and explain how hydrogen bonding influences boiling point, the solubility of molecules, and NMR and IR spectra. Results suggest that although students may be able to give appropriate definitions of hydrogen bonding and may recognize when this phenomenon can occur, significant numbers cannot apply their knowledge of hydrogen bonding to physical properties of molecules or to the interpretation of spectral data. Some possess misconceptions concerning boiling points and the ability of molecules to induce hydrogen bonding. Instructional strategies must be adjusted to address these issues.

Chemistry and physics

International Nuclear Information System (INIS)

Broerse, J.J.; Barendsen, G.W.; Kal, H.B.; Kogel, A.J. van der

1983-01-01

This book contains the extended abstracts of the contributions of the poster workshop sessions on chemistry and physics of the 7th international congress of radiation research. They cover the following main topics: primary processes in radiation physics and chemistry, general chemistry in radiation chemistry, DNA and model systems in radiation chemistry, molecules of biological interest in radiation chemistry, techniques in radiation chemistry, hot atom chemistry. refs.; figs.; tabs

Chemistry in space

CERN Document Server

Rehder, Dieter

2010-01-01

The dynamic field of extraterrestrial chemistry brings together ideas of chemistr, astrophysics, and biology to the study of molecules between stars, around stars, and on plantes. This book serves as an introduction to chemial processes under ?unearthly? and hence usually extreme conditions (temperature, pressure, high or low density, bombardment by cosmic rays), and their impact on the early development of our solar system, as well as providing a deeper understanding of processes in earthly regions where conditions approach those of extraterrestrial areas.A unique and extraordinary perspe

Heterogeneity within autism spectrum disorders: what have we learned from neuroimaging studies?

Directory of Open Access Journals (Sweden)

Rhoshel Krystyna Lenroot

2013-10-01

Full Text Available Autism spectrum disorders (ASD display significant heterogeneity. Although most neuroimaging studies in ASD have been designed to identify commonalities among affected individuals, rather than differences, some studies have explored variation within ASD. There have been two general types of approaches used for this in the neuroimaging literature to date: comparison of subgroups within ASD, and analyses using dimensional measures to link clinical variation to brain differences. This review focuses on structural and functional magnetic resonance imaging studies that have used these approaches to begin to explore heterogeneity between individuals with ASD. Although this type of data is yet sparse, recognition is growing of the limitations of behaviourally defined categorical diagnoses for understanding neurobiology. Study designs that are more informative regarding the sources of heterogeneity in ASD have the potential to improve our understanding of the neurobiological processes underlying ASD.

New Concept of C–H and C–C Bond Activation via Surface Organometallic Chemistry

KAUST Repository

Samantaray, Manoja

2015-08-18

In this chapter we describe the recent applications of well-defined oxidesupported metal alkyls/alkylidenes/alkylidynes and hydrides of group IV, V, and VI transition metals in the field of C–H and C–C bond activation. The activation of ubiquitous C–H and C–C bonds of paraffin is a long-standing challenge because of intrinsic low reactivity. There are many concepts derived from surface organometallic chemistry (SOMC): surface organometallic fragments are always intermediates in heterogeneous catalysis. The study of their synthesis and reactivity is a way to rationalize mechanism of heterogeneous catalysis and to achieve structure activity relationship. By surface organometallic chemistry one can enter any catalytic center by a reaction intermediate leading in fine to single site catalysts. With surface organometallic chemistry one can coordinate to the metal which can play a role in different elementary steps leading for example to C–H activation and Olefin metathesis. Because of the development of SOMC there is a lot of space for the improvement of homogeneous catalysis. After the 1997 discovery of alkane metathesis using silica-supported tantalum hydride by Basset et al. at low temperature (150ºC) the focus in this area was shifted to the discovery of more and more challenging surface complexes active in the application of C–H and C–C bond activation. Here we describe the evolution of well-defined metathesis catalyst with time as well as the effect of support on catalysis. We also describe here which metal–ligand combinations are responsible for a variety of C–H and C–C bond activation.

Intermediate-Scale Experimental Study to Improve Fundamental Understanding of Attenuation Capacity for Leaking CO2 in Heterogeneous Shallow Aquifers

Science.gov (United States)

Plampin, Michael R.; Porter, Mark L.; Pawar, Rajesh J.; Illangasekare, Tissa H.

2017-12-01

To assess the risks of Geologic Carbon Sequestration (GCS), it is crucial to understand the fundamental physicochemical processes that may occur if and when stored CO2 leaks upward from a deep storage reservoir into the shallow subsurface. Intermediate-scale experiments allow for improved understanding of the multiphase evolution processes that control CO2 migration behavior in the subsurface, because the boundary conditions, initial conditions, and porous media parameters can be better controlled and monitored in the laboratory than in field settings. For this study, a large experimental test bed was designed to mimic a cross section of a shallow aquifer with layered geologic heterogeneity. As water with aqueous CO2 was injected into the system to mimic a CO2-charged water leakage scenario, the spatiotemporal evolution of the multiphase CO2 plume was monitored. Similar experiments were performed with two different sand combinations to assess the relative effects of different types of geologic facies transitions on the CO2 evolution processes. Significant CO2 attenuation was observed in both scenarios, but by fundamentally different mechanisms. When the porous media layers had very different permeabilities, attenuation was caused by local accumulation (structural trapping) and slow redissolution of gas phase CO2. When the permeability difference between the layers was relatively small, on the other hand, gas phase continually evolved over widespread areas near the leading edge of the aqueous plume, which also attenuated CO2 migration. This improved process understanding will aid in the development of models that could be used for effective risk assessment and monitoring programs for GCS projects.

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-01

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes.

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-21

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

Operating experience in correcting severe secondary chemistry upsets by controlling makeup water organics (TOC)

International Nuclear Information System (INIS)

Flint, W.G.; Mc Intosh, R.J.

1986-01-01

In this paper following observations are presented: conductivity and chloride excursions in steam condensate were directly linked to makeup water quality. Data strongly suggests that the breakdown of makeup water organics was responsible for substandard condensate water quality; although the short-term effects of gross organic contamination have been documented, the longer term consequences of continuous exposure by moderate organic levels needs to be addressed; a greater understanding of the organic removal efficiency of the various water purification technologies is essential to controlling TOC contamination; and a much better understanding of makeup plant chemistry and the interrelationship of makeup water contamination and plant chemistry has proven essential to optimizing plant performance and guaranteeing the best possible steam chemistry. The role of the chemistry group as an active participant in operations has been proven at Kewaunee Nuclear Plant

Evaluation of the Influence of Wording Changes and Course Type on Motivation Instrument Functioning in Chemistry

Science.gov (United States)

Komperda, Regis; Hosbein, Kathryn N.; Barbera, Jack

2018-01-01

Increased understanding of the importance of the affective domain in chemistry education research has led to the development and adaptation of instruments to measure chemistry-specific affective traits, including motivation. Many of these instruments are adapted from other fields by using the word "chemistry" in place of other…

Global volcanic emissions: budgets, plume chemistry and impacts

Science.gov (United States)

Mather, T. A.

2012-12-01

Over the past few decades our understanding of global volcanic degassing budgets, plume chemistry and the impacts of volcanic emissions on our atmosphere and environment has been revolutionized. Global volcanic emissions budgets are needed if we are to make effective use of regional and global atmospheric models in order to understand the consequences of volcanic degassing on global environmental evolution. Traditionally volcanic SO2 budgets have been the best constrained but recent efforts have seen improvements in the quantification of the budgets of other environmentally important chemical species such as CO2, the halogens (including Br and I) and trace metals (including measurements relevant to trace metal atmospheric lifetimes and bioavailability). Recent measurements of reactive trace gas species in volcanic plumes have offered intriguing hints at the chemistry occurring in the hot environment at volcanic vents and during electrical discharges in ash-rich volcanic plumes. These reactive trace species have important consequences for gas plume chemistry and impacts, for example, in terms of the global fixed nitrogen budget, volcanically induced ozone destruction and particle fluxes to the atmosphere. Volcanically initiated atmospheric chemistry was likely to have been particularly important before biological (and latterly anthropogenic) processes started to dominate many geochemical cycles, with important consequences in terms of the evolution of the nitrogen cycle and the role of particles in modulating the Earth's climate. There are still many challenges and open questions to be addressed in this fascinating area of science.

From hot atom chemistry to epithermal chemistry

International Nuclear Information System (INIS)

Roessler, K.

2004-01-01

The rise and fall of hot atom chemistry (HAC) over the years from 1934 to 2004 is reviewed. Several applications are discussed, in particular to astrophysics and the interaction of energetic ions and atoms in space. Epithermal chemistry (ETC) is proposed to substitute the old name, since it better fits the energy range as well as the non-thermal and non-equilibrium character of the reactions. ETC also avoids the strong connexion of HAC to nuclear chemistry and stands for the opening of the field to physical chemistry and astrophysics. (orig.)

Mathematical Chemistry

OpenAIRE

Trinajstić, Nenad; Gutman, Ivan

2002-01-01

A brief description is given of the historical development of mathematics and chemistry. A path leading to the meeting of these two sciences is described. An attempt is made to define mathematical chemistry, and journals containing the term mathematical chemistry in their titles are noted. In conclusion, the statement is made that although chemistry is an experimental science aimed at preparing new compounds and materials, mathematics is very useful in chemistry, among other things, to produc...

Bubble and foam chemistry

CERN Document Server

Pugh, Robert J

2016-01-01

This indispensable guide will equip the reader with a thorough understanding of the field of foaming chemistry. Assuming only basic theoretical background knowledge, the book provides a straightforward introduction to the principles and properties of foams and foaming surfactants. It discusses the key ideas that underpin why foaming occurs, how it can be avoided and how different degrees of antifoaming can be achieved, and covers the latest test methods, including laboratory and industrial developed techniques. Detailing a variety of different kinds of foams, from wet detergents and food foams, to polymeric, material and metal foams, it connects theory to real-world applications and recent developments in foam research. Combining academic and industrial viewpoints, this book is the definitive stand-alone resource for researchers, students and industrialists working on foam technology, colloidal systems in the field of chemical engineering, fluid mechanics, physical chemistry, and applied physics.

Organic Chemistry in Space

Science.gov (United States)

Charnley, Steven

2009-01-01

Astronomical observations, theoretical modeling, laboratory simulation and analysis of extraterrestrial material have enhanced our knowledge of the inventory of organic matter in the interstellar medium (ISM) and on small bodies such as comets and asteroids (Ehrenfreund & Charnley 2000). Comets, asteroids and their fragments, meteorites and interplanetary dust particles (IDPs), contributed significant amounts of extraterrestrial organic matter to the young Earth. This material degraded and reacted in a terrestrial prebiotic chemistry to form organic structures that may have served as building blocks for life on the early Earth. In this talk I will summarize our current understanding of the organic composition and chemistry of interstellar clouds. Molecules of astrobiological relevance include the building blocks of our genetic material: nucleic acids, composed of subunits such as N-heterocycles (purines and pyrimidines), sugars and amino acids. Signatures indicative of inheritance of pristine and modified interstellar material in comets and meteorites will also be discussed.

Molecular surface science of heterogeneous catalysis. History and perspective

International Nuclear Information System (INIS)

Somorjai, G.A.

1983-08-01

A personal account is given of how the author became involved with modern surface science and how it was employed for studies of the chemistry of surfaces and heterogeneous catalysis. New techniques were developed for studying the properties of the surface monolayers: Auger electron spectroscopy, LEED, XPS, molecular beam surface scattering, etc. An apparatus was developed and used to study hydrocarbon conversion reactions on Pt, CO hydrogenation on Rh and Fe, and NH 3 synthesis on Fe. A model has been developed for the working Pt reforming catalyst. The three molecular ingredients that control catalytic properties are atomic surface structure, an active carbonaceous deposit, and the proper oxidation state of surface atoms. 40 references, 21 figures

Molecular surface science of heterogeneous catalysis. History and perspective

Energy Technology Data Exchange (ETDEWEB)

Somorjai, G.A.

1983-08-01

A personal account is given of how the author became involved with modern surface science and how it was employed for studies of the chemistry of surfaces and heterogeneous catalysis. New techniques were developed for studying the properties of the surface monolayers: Auger electron spectroscopy, LEED, XPS, molecular beam surface scattering, etc. An apparatus was developed and used to study hydrocarbon conversion reactions on Pt, CO hydrogenation on Rh and Fe, and NH/sub 3/ synthesis on Fe. A model has been developed for the working Pt reforming catalyst. The three molecular ingredients that control catalytic properties are atomic surface structure, an active carbonaceous deposit, and the proper oxidation state of surface atoms. 40 references, 21 figures. (DLC)

Physics of DNAPL Migration and Remediation in the Presence of Heterogeneities; TOPICAL

International Nuclear Information System (INIS)

CONRAD, STEPHEN H.; GLASS, ROBERT J.

1999-01-01

The goal of our research is to develop a fundamental quantitative understanding of the role of physical heterogeneities on DNAPL migration and remediation in aquifers. Such understanding is critical to cost effectively identify the location of the subsurface zone of contamination and design remediation schemes focused on removing the source of the contamination, the DNAPL itself. To reach this goal, the following objectives for the proposed research are defined: Objective 1: Develop fundamental understanding of the physics of DNAPL migration processes within heterogeneous porous media: (a) Conduct a suite of two-dimensional physical experiments within controlled and systematically varied heterogeneous porous media at scales up to one meter. Vary system parameters to consider a range of capillary and bond numbers within these heterogeneous porous structures. (b) Develop a new DNAPL migration model based on an up-scaling of invasion percolation (UP) to model the migration process. Compare the model predictions to experimental results. Accomplishing objective 1 provides a series of experiments against which we will be able to evaluate the validity of existing multi-phase flow theory as formulated in both percolation codes and in continuum flow codes. These experimental results will also provide new insights into DNAPL migration behavior. Development of the UIP model will provide an exciting alternative to continuum multi-phase flow codes since UIP offers several advantages for modeling DNAPL migration. The UIP model is fast, allowing for: (1) modeling in three dimensions; (2) the incorporation of much more geologic detail; and (3) its use in probabilistic modeling by way of Monte Carlo techniques. Objective 2: Develop fundamental understanding of the physics of DNAPL remediation processes within heterogeneous porous media: Conduct a suite of physical experiments within controlled and systematically varied heterogeneous porous media at scales up to one meter that

Spatial Reasoning and Understanding the Particulate Nature of Matter: A Middle School Perspective

Science.gov (United States)

Cole, Merryn L.

This dissertation employed a mixed-methods approach to examine the relationship between spatial reasoning ability and understanding of chemistry content for both middle school students and their science teachers. Spatial reasoning has been linked to success in learning STEM subjects (Wai, Lubinski, & Benbow, 2009). Previous studies have shown a correlation between understanding of chemistry content and spatial reasoning ability (e.g., Pribyl & Bodner, 1987; Wu & Shah, 2003: Stieff, 2013), raising the importance of developing the spatial reasoning ability of both teachers and students. Few studies examine middle school students' or in-service middle school teachers' understanding of chemistry concepts or its relation to spatial reasoning ability. The first paper in this dissertation addresses the quantitative relationship between mental rotation, a type of spatial reasoning ability, and understanding a fundamental concept in chemistry, the particulate nature of matter. The data showed a significant, positive correlation between scores on the Purdue Spatial Visualization Test of Rotations (PSVT; Bodner & Guay, 1997) and the Particulate Nature of Matter Assessment (ParNoMA; Yezierski, 2003) for middle school students prior to and after chemistry instruction. A significant difference in spatial ability among students choosing different answer choices on ParNoMA questions was also found. The second paper examined the ways in which students of different spatial abilities talked about matter and chemicals differently. Students with higher spatial ability tended to provide more of an explanation, though not necessarily in an articulate matter. In contrast, lower spatial ability students tended to use any keywords that seemed relevant, but provided little or no explanation. The third paper examined the relationship between mental reasoning and understanding chemistry for middle school science teachers. Similar to their students, a significant, positive correlation between

Heterogeneity in magnetic complex oxides

Science.gov (United States)

Arenholz, Elke

Heterogeneity of quantum materials on the nanoscale can result from the spontaneous formation of regions with distinct atomic, electronic and/or magnetic order, and indicates coexistence of competing quantum phases. In complex oxides, the subtle interplay of lattice, charge, orbital, and spin degrees of freedom gives rise to especially rich phase diagrams. For example, coexisting conducting and insulating phases can occur near metal-insulator transitions, colossal magnetoresistance can emerge where ferromagnetic and antiferromagnetic domains compete, and charge-ordered and superconducting regions are present simultaneously in materials exhibiting high-temperature superconductivity. Additionally, externally applied fields (electric, magnetic, or strain) or other external excitations (light or heat) can tip the energy balance towards one phase, or support heterogeneity and phase coexistence and provide the means to perturb and tailor quantum heterogeneity at the nanoscale. Engineering nanomaterials, with structural, electronic and magnetic characteristics beyond what is found in bulk materials, is possible today through the technique of thin film epitaxy, effectively a method of `spray painting' atoms on single crystalline substrates to create precisely customized layered structures with atomic arrangements defined by the underlying substrate. Charge transfer and spin polarization across interfaces as well as imprinting nanoscale heterogeneity between adjacent layers lead to intriguing and important new phenomena testing our understanding of basic physics and creating new functionalities. Moreover, the abrupt change of orientation of an order parameter between nanoscale domains can lead to unique phases that are localized at domain walls, including conducting domain walls in insulating ferroelectrics, and ferromagnetic domain walls in antiferromagnets. Here we present our recent results on tailoring the electronic anisotropy of multiferroic heterostructures by

Do High School Chemistry Examinations Inhibit Deeper Level Understanding of Dynamic Reversible Chemical Reactions?

Science.gov (United States)

Wheeldon, R.; Atkinson, R.; Dawes, A.; Levinson, R.

2012-01-01

Background and purpose: Chemistry examinations can favour the deployment of algorithmic procedures like Le Chatelier's Principle (LCP) rather than reasoning using chemical principles. This study investigated the explanatory resources which high school students use to answer equilibrium problems and whether the marks given for examination answers…

Contribution of water chemistry and fish condition to otolith chemistry: comparisons across salinity environments.

Science.gov (United States)

Izzo, C; Doubleday, Z A; Schultz, A G; Woodcock, S H; Gillanders, B M

2015-06-01

This study quantified the per cent contribution of water chemistry to otolith chemistry using enriched stable isotopes of strontium ((86) Sr) and barium ((137) Ba). Euryhaline barramundi Lates calcarifer, were reared in marine (salinity 40), estuarine (salinity 20) and freshwater (salinity 0) under different temperature treatments. To calculate the contribution of water to Sr and Ba in otoliths, enriched isotopes in the tank water and otoliths were quantified and fitted to isotope mixing models. Fulton's K and RNA:DNA were also measured to explore the influence of fish condition on sources of element uptake. Water was the predominant source of otolith Sr (between 65 and 99%) and Ba (between 64 and 89%) in all treatments, but contributions varied with temperature (for Ba), or interactively with temperature and salinity (for Sr). Fish condition indices were affected independently by the experimental rearing conditions, as RNA:DNA differed significantly among salinity treatments and Fulton's K was significantly different between temperature treatments. Regression analyses did not detect relations between fish condition and per cent contribution values. General linear models indicated that contributions from water chemistry to otolith chemistry were primarily influenced by temperature and secondly by fish condition, with a relatively minor influence of salinity. These results further the understanding of factors that affect otolith element uptake, highlighting the necessity to consider the influence of environment and fish condition when interpreting otolith element data to reconstruct the environmental histories of fish. © 2015 The Fisheries Society of the British Isles.

Critical Chemistry Education in a Private, Suburban High School

Science.gov (United States)

Ashby, Patrick; Mensah, Felicia Moore

2018-01-01

This critical ethnography documents how a group of 25 students and their teacher/researcher in a suburban, private school setting, the vast majority from the dominant cultural background, engaged with and enacted a critical chemistry education together. Critical chemistry education contextualizes chemistry in socially relevant issues and problematizes participants' conceptual frameworks for understanding the intersections between chemistry and our capitalist society by identifying the shortcomings of traditional scientific language to sufficiently interrogate privilege and oppression. Qualitative data from teacher/researcher field notes and journal, classroom video transcripts, questionnaires, focus group interviews, and student artifacts document that while it is difficult for the teacher/researcher and the students of this setting to reflect upon their own positions of privilege, together they interpreted and made meaning of their experience by (1) developing the ability to critically analyze the products of science for the potential of oppression, (2) developing an understanding of inequity in science, and (3) evaluating and respecting diverse knowledge bases. Based on the findings, we suggest students should be encouraged to problematize socially situated science issues related to settings close to their own communities, students should participate in structured and purposeful journaling to improve their metacognition and critical reflexivity, and critical pedagogues must be explicit with students in their Marxist-based interpretation of the global capitalist super structure.

Workshop report on large-scale matrix diagonalization methods in chemistry theory institute

Energy Technology Data Exchange (ETDEWEB)

Bischof, C.H.; Shepard, R.L.; Huss-Lederman, S. [eds.

1996-10-01

The Large-Scale Matrix Diagonalization Methods in Chemistry theory institute brought together 41 computational chemists and numerical analysts. The goal was to understand the needs of the computational chemistry community in problems that utilize matrix diagonalization techniques. This was accomplished by reviewing the current state of the art and looking toward future directions in matrix diagonalization techniques. This institute occurred about 20 years after a related meeting of similar size. During those 20 years the Davidson method continued to dominate the problem of finding a few extremal eigenvalues for many computational chemistry problems. Work on non-diagonally dominant and non-Hermitian problems as well as parallel computing has also brought new methods to bear. The changes and similarities in problems and methods over the past two decades offered an interesting viewpoint for the success in this area. One important area covered by the talks was overviews of the source and nature of the chemistry problems. The numerical analysts were uniformly grateful for the efforts to convey a better understanding of the problems and issues faced in computational chemistry. An important outcome was an understanding of the wide range of eigenproblems encountered in computational chemistry. The workshop covered problems involving self- consistent-field (SCF), configuration interaction (CI), intramolecular vibrational relaxation (IVR), and scattering problems. In atomic structure calculations using the Hartree-Fock method (SCF), the symmetric matrices can range from order hundreds to thousands. These matrices often include large clusters of eigenvalues which can be as much as 25% of the spectrum. However, if Cl methods are also used, the matrix size can be between 10{sup 4} and 10{sup 9} where only one or a few extremal eigenvalues and eigenvectors are needed. Working with very large matrices has lead to the development of

NATO Advanced Research Workshop on The Chemistry of Weathering

CERN Document Server

1985-01-01

Several important developments in our understanding of the chemistry of weathering have occurred in the last few years: 1. There has been a major breakthrough in our understanding of the mechanisms controlling the kinetics of sil icate dissolution, and there have been major advances in computer modeling of weathering processes. 2. There has been a growing recognition of the importance of organic solutes in the weathering process, and hence of the inter-relationships between mineral weathering and the terrestrial ecosystem. 3. The impact of acid deposition ("acid rain") has been widely recognized. The processes by which acid deposition is neutral ized are closely related to the processes of normal chemical weathering; an understanding of the chemistry of weathering is thus essential for predicting the effects of acid deposition. 4. More high-qual ity data have become available on the chemical dynamics of smal I watersheds and large river systems, which represent the integrated effects of chemical weathering.

Application of physical adsorption thermodynamics to heterogeneous chemistry on polar stratospheric clouds

Science.gov (United States)

Elliott, Scott; Turco, Richard P.; Toon, Owen B.; Hamill, Patrick

1991-01-01

Laboratory isotherms for the binding of several nonheterogeneously active atmospheric gases and for HCl to water ice are translated into adsorptive equilibrium constants and surface enthalpies. Extrapolation to polar conditions through the Clausius Clapeyron relation yields coverage estimates below the percent level for N2, Ar, CO2, and CO, suggesting that the crystal faces of type II stratospheric cloud particles may be regarded as clean with respect to these species. For HCl, and perhaps HF and HNO3, estimates rise to several percent, and the adsorbed layer may offer acid or proton sources alternate to the bulk solid for heterogeneous reactions with stratospheric nitrates. Measurements are lacking for many key atmospheric molecules on water ice, and almost entirely for nitric acid trihydrate as substrate. Adsorptive equilibria enter into gas to particle mass flux descriptions, and the binding energy determines rates for desorption of, and encounter between, potential surface reactants.

Understanding the acquisition and regulation mechanisms of the water chemistry in a clay formation: the CEC/ANDRA Archimede-argile project

International Nuclear Information System (INIS)

Merceron, T.; Mossmann, J.R.; Neerdael, B.; Canniere, P. de; Beaucaire, C.; Toulhoat, P.; Daumas, S.; Bianchi, A.; Christen, R.

1993-01-01

Clay formations are candidate host environments to high level radioactive waste repository. The radioelements could be partially released from the waste into the host geological formation after a very long time. Understanding behaviour of the natural chemical species is considered as a fundamental prerequisite before the disturbed system will be studied. Additional laboratory studies are also essential in order to forecast, by analogy, the behaviour of radioelements released from the radioactive waste repository. The ARCHIMEDE-ARGILE project has two main goals. The first is to gain an understanding of the mechanisms of acquisition and regulation of the water chemistry in a clay environment. This step is essential to predict both the behaviour and the migration in solution of artificial elements which are initially absent in the clay formation. The second is to test and validate in clay the measured physico chemical parameters which are the basis for the geochemical modelling of the behaviour of the natural and artificial radioelements. The paper presents the main results previously obtained on granitic waters and the research strategy established for the ARCHIMEDE project. (authors). 2 figs., 2 refs

Radiation chemistry of amino acids and peptides in aqueous solutions

International Nuclear Information System (INIS)

Simic, M.G.

1978-01-01

Radiation chemistry relevant to radiation preservation of high protein foods is reviewed. Some conclusions concerning the chemistry of irradiated amino acids, peptides, and proteins have been derived from product analysis of γ-irradiated solutions while the main mechanistic considerations result from the chemistry and kinetics of free radical intermediates observed by pulse radiolysis. The precursors of chemistry in not too concentrated solutions ( - , OH, and H. Their reactivity with molecules and their preference for characteristic groups within the molecule are discussed. The reviewed reactions of the model systems are accountable for a variety of radiolytic products found in irradiated foods. From detailed understanding of radiation chemistry in aqueous and frozen systems formation of many classes of compounds can be predicted or entirely eliminated in order to corroborate and extend the conclusions reached from the animal feeding experiments concerning the formation of toxic, mutagenic, and carcinogenic compounds and/or reduction of the nutritional value of foods

Modeling UTLS water vapor: Transport/Chemistry interactions

International Nuclear Information System (INIS)

Gulstad, Line

2005-01-01

This thesis was initially meant to be a study on the impact on chemistry and climate from UTLS water vapor. However, the complexity of the UTLS water vapor and its recent changes turned out to be a challenge by it self. In the light of this, the overall motivation for the thesis became to study the processes controlling UTLS water vapor and its changes. Water vapor is the most important greenhouse gas, involved in important climate feedback loops. Thus, a good understanding of the chemical and dynamical behavior of water vapor in the atmosphere is crucial for understanding the climate changes in the last century. Additionally, parts of the work was motivated by the development of a coupled climate chemistry model based on the CAM3 model coupled with the Chemical Transport Model Oslo CTM2. The future work will be concentrated on the UTLS water vapor impact on chemistry and climate. We are currently studying long term trends in UTLS water vapor, focusing on identification of the different processes involved in the determination of such trends. The study is based on natural as well as anthropogenic climate forcings. The ongoing work on the development of a coupled climate chemistry model will continue within our group, in collaboration with Prof. Wei-Chyung Wang at the State University of New York, Albany. Valuable contacts with observational groups are established during the work on this thesis. These collaborations will be continued focusing on continuous model validation, as well as identification of trends and new features in UTLS water vapor, and other tracers in this region. (Author)

Heterogeneous Ice Nucleation: Interplay of Surface Properties and Their Impact on Water Orientations.

Science.gov (United States)

Glatz, Brittany; Sarupria, Sapna

2018-01-23

Ice is ubiquitous in nature, and heterogeneous ice nucleation is the most common pathway of ice formation. How surface properties affect the propensity to observe ice nucleation on that surface remains an open question. We present results of molecular dynamics studies of heterogeneous ice nucleation on model surfaces. The models surfaces considered emulate the chemistry of kaolinite, an abundant component of mineral dust. We investigate the interplay of surface lattice and hydrogen bonding properties in affecting ice nucleation. We find that lattice matching and hydrogen bonding are necessary but not sufficient conditions for observing ice nucleation at these surfaces. We correlate this behavior to the orientations sampled by the metastable supercooled water in contact with the surfaces. We find that ice is observed in cases where water molecules not only sample orientations favorable for bilayer formation but also do not sample unfavorable orientations. This distribution depends on both surface-water and water-water interactions and can change with subtle modifications to the surface properties. Our results provide insights into the diverse behavior of ice nucleation observed at different surfaces and highlight the complexity in elucidating heterogeneous ice nucleation.

Principles of Chemistry (by Michael Munowitz)

Science.gov (United States)

Kovac, Reviewed By Jeffrey

2000-05-01

At a time when almost all general chemistry textbooks seem to have become commodities designed by marketing departments to offend no one, it is refreshing to find a book with a unique perspective. Michael Munowitz has written what I can only describe as a delightful chemistry book, full of conceptual insight, that uses a novel and interesting pedagogic strategy. This is a book that has much to recommend it. This is the best-written general chemistry book I have ever read. An editor with whom I have worked recently remarked that he felt his job was to help authors make their writing sing. Well, the writing in Principles of Chemistry sings with the full, rich harmonies and creative inventiveness of the King's Singers or Chanticleer. Here is the first sentence of the introduction: "Central to any understanding of the physical world is one discovery of paramount importance, a truth disarmingly simple yet profound in its implications: matter is not continuous." This is prose to be savored and celebrated. Principles of Chemistry has a distinct perspective on chemistry: the perspective of the physical chemist. The focus is on simplicity, what is common about molecules and reactions; begin with the microscopic and build bridges to the macroscopic. The author's perspective is clear from the organization of the book. After three rather broad introductory chapters, there are four chapters that develop the quantum mechanical theory of atoms and molecules, including a strong treatment of molecular orbital theory. Unlike many books, Principles of Chemistry presents the molecular orbital approach first and introduces valence bond theory later only as an approximation for dealing with more complicated molecules. The usual chapters on descriptive inorganic chemistry are absent (though there is an excellent chapter on organic and biological molecules and reactions as well as one on transition metal complexes). Instead, descriptive chemistry is integrated into the development of

Understanding Gas-Phase Ammonia Chemistry in Protoplanetary Disks

Science.gov (United States)

Chambers, Lauren; Oberg, Karin I.; Cleeves, Lauren Ilsedore

2017-01-01

Protoplanetary disks are dynamic regions of gas and dust around young stars, the remnants of star formation, that evolve and coagulate over millions of years in order to ultimately form planets. The chemical composition of protoplanetary disks is affected by both the chemical and physical conditions in which they develop, including the initial molecular abundances in the birth cloud, the spectrum and intensity of radiation from the host star and nearby systems, and mixing and turbulence within the disk. A more complete understanding of the chemical evolution of disks enables a more complete understanding of the chemical composition of planets that may form within them, and of their capability to support life. One element known to be essential for life on Earth is nitrogen, which often is present in the form of ammonia (NH3). Recent observations by Salinas et al. (2016) reveal a theoretical discrepancy in the gas-phase and ice-phase ammonia abundances in protoplanetary disks; while observations of comets and protostars estimate the ice-phase NH3/H2O ratio in disks to be 5%, Salinas reports a gas-phase NH3/H2O ratio of ~7-84% in the disk surrounding TW Hydra, a young nearby star. Through computational chemical modeling of the TW Hydra disk using a reaction network of over 5000 chemical reactions, I am investigating the possible sources of excess gas-phase NH3 by determining the primary reaction pathways of NH3 production; the downstream chemical effects of ionization by ultraviolet photons, X-rays, and cosmic rays; and the effects of altering the initial abundances of key molecules such as N and N2. Beyond providing a theoretical explanation for the NH3 ice/gas discrepancy, this new model may lead to fuller understanding of the gas-phase formation processes of all nitrogen hydrides (NHx), and thus fuller understanding of the nitrogen-bearing molecules that are fundamental for life as we know it.

Industrial chemistry engineering

International Nuclear Information System (INIS)

1993-01-01

This book on industrial chemistry engineering is divided in two parts. The first part deals with industrial chemistry, inorganic industrial chemistry, organic industrial chemistry, analytical chemistry and practical questions. The last parts explain the chemical industry, a unit parts and thermodynamics in chemical industry and reference. It reveals the test subjects for the industrial chemistry engineering with a written examination and practical skill.

2017 Atmospheric Chemistry Gordon Research Conference

Science.gov (United States)

2017-11-13

am - 10:45 am Discussion 10:45 am - 11:05 am Coffee Break 11:05 am - 11:35 am Allison Steiner (University of Michigan, USA) "The Atmospheric Life ...34Progress and Prospects: The Quest to Understand the Impacts of Multiphase Chemistry on a Wet Planet " 11:35 am - 11:50 am Discussion 11:50 am - 12:00

Advanced chemistry management system to optimize BWR chemistry control

International Nuclear Information System (INIS)

Maeda, K.; Nagasawa, K.

2002-01-01

BWR plant chemistry control has close relationships among nuclear safety, component reliability, radiation field management and fuel integrity. Advanced technology is required to improve chemistry control [1,3,6,7,10,11]. Toshiba has developed TACMAN (Toshiba Advanced Chemistry Management system) to support BWR chemistry control. The TACMAN has been developed as response to utilities' years of requirements to keep plant operation safety, reliability and cost benefit. The advanced technology built into the TACMAN allows utilities to make efficient chemistry control and to keep cost benefit. TACMAN is currently being used in response to the needs for tools those plant chemists and engineers could use to optimize and identify plant chemistry conditions continuously. If an incipient condition or anomaly is detected at early stage, root causes evaluation and immediate countermeasures can be provided. Especially, the expert system brings numerous and competitive advantages not only to improve plant chemistry reliability but also to standardize and systematize know-how, empirical knowledge and technologies in BWR chemistry This paper shows detail functions of TACMAN and practical results to evaluate actual plant. (authors)

chemistry teachers and their senior secondary students' answers

African Journals Online (AJOL)

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STUDENTS' ANSWERS TO PICTORIAL AND VERBAL QUESTIONS IN. EVAPORATION ... chemical education have since changed focus along this direction. ... achievement on the conceptual understanding test in chemistry. Teachers feel ..... Nurrenbern, S. C. & Pickering, M. (1987) Two Kinds of Conceptual Problems in.

Modeling the Explicit Chemistry of Anthropogenic and Biogenic Organic Aerosols

Energy Technology Data Exchange (ETDEWEB)

Madronich, Sasha [Univ. Corporation for Atmospheric Research, Boulder, CO (United States)

2015-12-09

The atmospheric burden of Secondary Organic Aerosols (SOA) remains one of the most important yet uncertain aspects of the radiative forcing of climate. This grant focused on improving our quantitative understanding of SOA formation and evolution, by developing, applying, and improving a highly detailed model of atmospheric organic chemistry, the Generation of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) model. Eleven (11) publications have resulted from this grant.

REFLECTIVE APPROACH IN TEACHING PRE-DEGREE CHEMISTRY

Directory of Open Access Journals (Sweden)

B. Venkateswara RAO

2009-04-01

Full Text Available The study is a component of a larger investigation that focuses on exemplary practice in chemistry education. This case study involves an investigation of a chemistry teacher in two years intermediate education in Vijayawada, Andhra Pradesh, India. The study utilized an interpretive methodology in which the questions emerged from intensive observations of chemistry lessons in classes taught by a teacher. The principal finding was that a teacher focused on teaching for understanding. Once teacher tended to emphasize whole-class activities while the other times he utilized more small-group and individualized activities. The teacher was successful in his goal of teaching for understanding because he was effective classroom manager and he had strong science content knowledge that enabled him to focus on instructional strategies that facilitated student understanding. He asked appropriate questions, responded to student questions, and used effective cognitive monitoring strategies. The teacher was able to teach effectively because he had adequate content knowledge and pedagogical content knowledge. Researcher adopted the method of action research to class room teaching where a classroom event triggers the process of reflection followed by critical analysis of the event which leads to change and subsequent reflection to observe that change and so on. He has taken two different texts to teach students. Out of two texts, one is explaining the metallurgy of Magnesium. In that case, he was successful as a teacher when he adopted comparative method of teaching metallurgy of Magnesium rather than the traditional method of teaching. The other one is explaining the properties of Hydrogen peroxide. In this case he was successful as a teacher by adopting discussion, interaction and discussion method.

Current organic chemistry

National Research Council Canada - National Science Library

1997-01-01

Provides in depth reviews on current progress in the fields of asymmetric synthesis, organometallic chemistry, bioorganic chemistry, heterocyclic chemistry, natural product chemistry, and analytical...

Measuring Meaningful Learning in the Undergraduate Chemistry Laboratory: A National, Cross-Sectional Study

Science.gov (United States)

Galloway, Kelli R.; Bretz, Stacey Lowery

2015-01-01

Research on laboratory learning points to the need to better understand what and how students learn in the undergraduate chemistry laboratory. The Meaningful Learning in the Laboratory Instrument (MLLI) was administered to general and organic chemistry students from 15 colleges and universities across the United States in order to measure the…

Aquatic Chemistry

International Nuclear Information System (INIS)

Kim, Dong Yeun; Kim, Oh Sik; Kim, Chang Guk; Park, Cheong Gil; Lee, Gwi Hyeon; Lee, Cheol Hui

1987-07-01

This book deals aquatic chemistry, which treats water and environment, chemical kinetics, chemical balance like dynamical characteristic, and thermodynamics, acid-base chemistry such as summary, definition, kinetics, and PH design for mixture of acid-base chemistry, complex chemistry with definition, and kinetics, precipitation and dissolution on summary, kinetics of precipitation and dissolution, and balance design oxidation and resolution with summary, balance of oxidation and resolution.

Combinatorial chemistry

DEFF Research Database (Denmark)

Nielsen, John

1994-01-01

An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds.......An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds....

Forensic Chemistry

Science.gov (United States)

Bell, Suzanne

2009-07-01

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

Chemistry-nuclear chemistry division. Progress report, October 1979-September 1980

International Nuclear Information System (INIS)

Ryan, R.R.

1981-05-01

This report presents the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, element migration and fixation, inorganic chemistry, isotope separation and analysis, atomic and molecular collisions, molecular spectroscopy, muonic x rays, nuclear cosmochemistry, nuclear structure and reactions, radiochemical separations, theoretical chemistry, and unclassified weapons research

Chemistry-nuclear chemistry division. Progress report, October 1979-September 1980

Energy Technology Data Exchange (ETDEWEB)

Ryan, R.R. (comp.)

1981-05-01

This report presents the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, element migration and fixation, inorganic chemistry, isotope separation and analysis, atomic and molecular collisions, molecular spectroscopy, muonic x rays, nuclear cosmochemistry, nuclear structure and reactions, radiochemical separations, theoretical chemistry, and unclassified weapons research.

Fuel Chemistry Division: progress report for 1985

International Nuclear Information System (INIS)

1988-01-01

Fuel Chemistry Division was formed in May 1985 to give a larger emphasis on the research and development in chemistry of the nuclear fuel cycle. The areas of research in Fuel Chemistry Division are fuel development and its chemical quality control, understanding of the fuel behaviour and post irradiation examinations, chemistry of reprocessing and waste management processes as also the basic aspects of actinide and relevant fission product elements. This report summarises the work by the staff of the Division during 1985 and also some work from the previous periods which was not reported in the progress reports of the Radiochemistry Division. The work related to the FBTR fuel was one of the highlights during this period. In the area of process chemistry useful work has been carried out for processing of plutonium bearing solutions. In the area of mass spectrometry, the determination of trace constituents by spark source mass spectrometry has been a major area of research. Significant progress has also been made in the use of alpha spectromet ry techniques for the determination of plutonium in dissolver solution and other samples. The technology of plutonium utilisation is quite complex and the Division would continue to look into the chemical aspects of this technology and provide the necessary base for future developments in this area. (author)

Pre-University Chemistry Students in a Mimicked Scholarly Peer Review

Science.gov (United States)

van Rens, Lisette; Hermarij, Philip; Pilot, Albert; Beishuizen, Jos; Hofman, Herman; Wal, Marjolein

2014-01-01

Peer review is a significant component in scientific research. Introducing peer review into inquiry processes may be regarded as an aim to develop student understanding regarding quality in inquiries. This study examines student understanding in inquiry peer reviews among pre-university chemistry students, aged 16-17, when they enact a design of a…

Non-Coding Transcript Heterogeneity in Mesothelioma: Insights from Asbestos-Exposed Mice.

Science.gov (United States)

Felley-Bosco, Emanuela; Rehrauer, Hubert

2018-04-11

Mesothelioma is an aggressive, rapidly fatal cancer and a better understanding of its molecular heterogeneity may help with making more efficient therapeutic strategies. Non-coding RNAs represent a larger part of the transcriptome but their contribution to diseases is not fully understood yet. We used recently obtained RNA-seq data from asbestos-exposed mice and performed data mining of publicly available datasets in order to evaluate how non-coding RNA contribute to mesothelioma heterogeneity. Nine non-coding RNAs are specifically elevated in mesothelioma tumors and contribute to human mesothelioma heterogeneity. Because some of them have known oncogenic properties, this study supports the concept of non-coding RNAs as cancer progenitor genes.

Heterogeneous precipitation of niobium carbide in the ferrite by Monte Carlo simulations; Cinetique de precipitation heterogene du carbure de niobium dans la ferrite

Energy Technology Data Exchange (ETDEWEB)

Hin, C

2005-12-15

The precipitation of niobium carbides in industrial steels is commonly used to control the recrystallization process or the amount of interstitial atoms in solid solution. It is then important to understand the precipitation kinetics and especially the competition between homogeneous and heterogeneous precipitation, since both of them have been observed experimentally, depending on they alloy composition, microstructure and thermal treatments. We propose Monte Carlo simulations of NbC precipitation in {open_square}-iron, based on a simple atomic description of the main parameters which control the kinetic pathway: - Realistic diffusion properties, with a rapid diffusion of C atoms by interstitial jumps and a slower diffusion of Fe and Nb atoms by vacancy jumps; - A model of grain boundaries which reproduces the segregation properties of Nb and C; - A model of dislocation which interacts with solute atoms through local segregation energies and long range elastic field; - A point defect source which drives the vacancy concentration towards its equilibrium value. Depending on the precipitation conditions, Monte Carlo simulations predict different kinetic behaviors, including a transient precipitation of metastable carbides, an early segregation stage of C, wetting phenomena at grain boundaries and on dislocations and a competition between homogeneous and heterogeneous NbC precipitation. Concerning the last point, we highlight that long range elastic field due to dislocation favors clearly the heterogeneous precipitation on dislocations. To understand this effect, we have developed a heterogeneous nucleation model including the calculation of the local concentration of solute atoms around the dislocation, the change of the solubility limit relative to the solubility limit in bulk and the energy of precipitates in an elastic field. We have concluded that elastic field favors the heterogeneous precipitation through the fall in nucleation barrier. (author)

Plutonium(IV) hydrous polymer chemistry

International Nuclear Information System (INIS)

Toth, L.M.; Dodson, K.E.

1985-01-01

The hydrous polymer chemistry of Pu(IV) in aqueous nitric acid solutions has been a subject of considerable interest for several years. This interest stems mainly from the fact that most nuclear fuel reprocessing schemes based on the Purex process can be hampered by the occurrence of polymer. As a result, an understanding and control of the parameters that affect polymer formation during reprocessing are studied. 2 refs

Molecular Structure of Salt Solutions: A New View of the Interface with Implications for Heterogeneous Atmospheric Chemistry

Czech Academy of Sciences Publication Activity Database

Jungwirth, Pavel; Tobias, D. J.

2001-01-01

Roč. 105, č. 43 (2001), s. 10468-10472 ISSN 1089-5647 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : air-solution interface * salt solutions * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.379, year: 2001

The Brazilian medicinal chemistry from 1998 to 2008 in the Journal of Medicinal Chemistry, Bioorganic and Medicinal Chemistry, Bioorganic and Medicinal Chemistry Letters and European Journal of Medicinal Chemistry [A química medicinal brasileira de 1998 a 2008 nos periódicos Journal of Medicinal Chemistry, Bioorganic and Medicinal Chemistry, Bioorganic and Medicinal Chemistry Letters e European Journal of Medicinal Chemistry

OpenAIRE

Bárbara Vasconcellos da Silva; Renato Saldanha Bastos; Angelo da Cunha Pinto

2009-01-01

In this article we present the Brazilian publications, the research groups involved, the contributions per states and the main diseases studied from 1998 to 2008 in the following periodicals: Journal of Medicinal Chemistry, Bioorganic and Medicinal Chemistry, Bioorganic and Medicinal Chemistry Letters and European Journal of Medicinal Chemistry.

The heterogeneity of wooded-agricultural landscape mosaics influences woodland bird community assemblages

OpenAIRE

Neumann, Jessica L.; Griffiths, Geoffrey H.; Foster, Christopher W.; Holloway, Graham J.

2016-01-01

Context\\ud Landscape heterogeneity (the composition and configuration of different landcover types) plays a key role in shaping woodland bird assemblages in wooded-agricultural mosaics. Understanding how species respond to landscape factors could contribute to preventing further decline of woodland bird populations.\\ud Objective\\ud To investigate how woodland birds with different species traits respond to landscape heterogeneity, and to identify whether specific landcover types are important ...

Understanding LiOH chemistry in a ruthenium-catalyzed Li-O{sub 2} battery

Energy Technology Data Exchange (ETDEWEB)

Liu, Tao; Liu, Zigeng; Kim, Gunwoo; Grey, Clare P. [Department of Chemistry, University of Cambridge (United Kingdom); Frith, James T.; Garcia-Araez, Nuria [Department of Chemistry, University of Southampton (United Kingdom)

2017-12-11

Non-aqueous Li-O{sub 2} batteries are promising for next-generation energy storage. New battery chemistries based on LiOH, rather than Li{sub 2}O{sub 2}, have been recently reported in systems with added water, one using a soluble additive LiI and the other using solid Ru catalysts. Here, the focus is on the mechanism of Ru-catalyzed LiOH chemistry. Using nuclear magnetic resonance, operando electrochemical pressure measurements, and mass spectrometry, it is shown that on discharging LiOH forms via a 4 e{sup -} oxygen reduction reaction, the H in LiOH coming solely from added H{sub 2}O and the O from both O{sub 2} and H{sub 2}O. On charging, quantitative LiOH oxidation occurs at 3.1 V, with O being trapped in a form of dimethyl sulfone in the electrolyte. Compared to Li{sub 2}O{sub 2}, LiOH formation over Ru incurs few side reactions, a critical advantage for developing a long-lived battery. An optimized metal-catalyst-electrolyte couple needs to be sought that aids LiOH oxidation and is stable towards attack by hydroxyl radicals. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Phase diagrams and heterogeneous equilibria a practical introduction

CERN Document Server

Predel, Bruno; Pool, Monte

2004-01-01

This graduate-level textbook provides an introduction to the practical application of phase diagrams. It is intended for students and researchers in chemistry, metallurgy, mineralogy, and materials science as well as in engineering and physics. Heterogeneous equilibria are described by a minimum of theory illustrated by practical examples and realistic case discussions from the different fields of application. The treatment of the physical and energetic background of phase equilibria leads to the discussion of the thermodynamics of mixtures and the correlation between energetics and composition. Thus, tools for the prediction of energetic, structural, and physical quantities are provided. The authors treat the nucleation of phase transitions, the production and stability of technologically important metastable phases, and metallic glasses. Furthermore, the text also concisely presents the thermodynamics and composition of polymer systems.

Radiation chemistry and its applications

International Nuclear Information System (INIS)

1968-01-01

In recent years considerable progress has been made in understanding the fundamental chemical reactions that occur when materials are irradiated. This has followed from the development of new techniques for studying these reactions. The International Atomic Energy Agency held a Panel on Radiation Chemistry in Vienna on 17-21 April 1967, to review the current status of various sources, new techniques in radiation chemistry, and their applications. The main sources mentioned by the Panel were isotope sources, electron accelerators, and chemonuclear reactors. Among the basic techniques discussed were pulsed radiolysis, flash photolysis, fast ESR methods, irradiation at liquid helium temperatures, electric discharge methods and far ultra-violet methods. Interesting industrial applications were discussed, such as the development of wood-plastic combinations, and a paper was given on the curing of paints and thin films Refs, figs and tabs

Bio-organic chemistry at BARC

International Nuclear Information System (INIS)

Sharma, A.; Ghosh, S.K.; Chattopadhyay, S.

2009-01-01

Bioorganic chemistry plays a pivotal role of co-ordination amongst the research and developmental activities of physical, biological, material and nuclear sciences. Understandably, the domain of bioorganic chemistry encompasses overlapping scientific fields, and often involves multi-disciplinary subjects. The research activities of bioorganic research at BARC are, therefore directed with reference to deliverables, relevant to various nuclear and non-nuclear programmes of the department. Also, the activities of the division are fine tuned to address the contemporary needs. It is now well recognized that organic compounds are essential in various programmes of nuclear technology. These include solvents and membranes for the back-end process, carrier molecules for radiopharmaceuticals, optoelectrical materials and sensors for high tech applications etc. Coupled with this, bioorganics also form integral part of the departmental mission-oriented societal programmes in the areas of health and agriculture

Areas of research in radiation chemistry fundamental to radiation biology

International Nuclear Information System (INIS)

Powers, E.L.

1980-01-01

Among all the environmental hazards to which man is exposed, ionizing radiation is the most thoroughly investigated and the most responsibly monitored and controlled. Nevertheless, because of the importance of radiation in modern society from both the hazard as well as the utilitarian standpoints, much more information concerning the biological effects induced and their modification and reversal is required. Together with radiation physics, an understanding of radiation chemistry is necessary for full appreciation of biological effects of high and low energy radiations, and for the development of prophylactic, therapeutic and potentiating methods and techniques in biological organisms. The necessity of understanding the chemistry of any system, biological or not, that is to be manipulated and controlled, is so obvious as to make trivial a statement to that effect. If any natural phenomenon is to be put to our use, surely the elements of it must be studied and appreciated fully. In the preliminary statements of the various panels of this general group, the need for additional information on the basic radiation chemistry concerned in radiation-induced biological effects pervades throughout

Kraft lignin chain extension chemistry via propargylation, oxidative coupling, and Claisen rearrangement.

Science.gov (United States)

Sen, Sanghamitra; Sadeghifar, Hasan; Argyropoulos, Dimitris S

2013-10-14

Despite its aromatic and polymeric nature, the heterogeneous, stochastic, and reactive characteristics of softwood kraft lignin seriously limit its potential for thermoplastic applications. Our continuing efforts toward creating thermoplastic lignin polymers are now focused at exploring propargylation derivatization chemistry and its potential as a versatile novel route for the eventual utilization of technical lignins with a significant amount of molecular control. To do this, we initially report the systematic propargylation of softwood kraft lignin. The synthesized derivatives were extensively characterized with thermal methods (DSC, TGA), (1)H, (13)C, and quantitative (31)P NMR and IR spectroscopies. Further on, we explore the versatile nature of the lignin pendant propargyl groups by demonstrating two distinct chain extension chemistries; the solution-based, copper-mediated, oxidative coupling and the thermally induced, solid-state, Claissen rearrangement polymerization chemistries. Overall, we show that it is possible to modulate the reactivity of softwood kraft lignin via a combination of methylation and chain extension providing a rational means for the creation of higher molecular weight polymers with the potential for thermoplastic materials and carbon fibers with the desired control of structure-property relations.

Bad chemistry

OpenAIRE

Petsko, Gregory A

2004-01-01

General chemistry courses haven't changed significantly in forty years. Because most basic chemistry students are premedical students, medical schools have enormous influence and could help us start all over again to create undergraduate chemistry education that works.

Organic Chemistry Students' Ideas about Nucleophiles and Electrophiles: The Role of Charges and Mechanisms

Science.gov (United States)

Anzovino, Mary E.; Bretz, Stacey Lowery

2015-01-01

Organic chemistry students struggle with reaction mechanisms and the electron-pushing formalism (EPF) used by practicing organic chemists. Faculty have identified an understanding of nucleophiles and electrophiles as one conceptual prerequisite to mastery of the EPF, but little is known about organic chemistry students' knowledge of nucleophiles…

Positronium chemistry

CERN Document Server

Green, James

1964-01-01

Positronium Chemistry focuses on the methodologies, reactions, processes, and transformations involved in positronium chemistry. The publication first offers information on positrons and positronium and experimental methods, including mesonic atoms, angular correlation measurements, annihilation spectra, and statistical errors in delayed coincidence measurements. The text then ponders on positrons in gases and solids. The manuscript takes a look at the theoretical chemistry of positronium and positronium chemistry in gases. Topics include quenching, annihilation spectrum, delayed coincidence

Characterizing Normal Groundwater Chemistry in Hawaii

Science.gov (United States)

Tachera, D.; Lautze, N. C.; Thomas, D. M.; Whittier, R. B.; Frazer, L. N.

2017-12-01

Hawaii is dependent on groundwater resources, yet how water moves through the subsurface is not well understood in many locations across the state. As marine air moves across the islands water evaporates from the ocean, along with trace amounts of sea-salt ions, and interacts with the anthropogenic and volcanic aerosols (e.g. sulfuric acid, ammonium sulfate, HCl), creating a slightly more acidic rain. When this rain falls, it has a chemical signature distinctive of past processes. As this precipitation infiltrates through soil it may pick up another distinctive chemical signature associated with land use and degree of soil development, and as it flows through the underlying geology, its chemistry is influenced by the host rock. We are currently conducting an investigation of groundwater chemistry in selected aquifer areas of Hawaii, having diverse land use, land cover, and soil development conditions, in an effort to investigate and document what may be considered a "normal" water chemistry for an area. Through this effort, we believe we better assess anomalies due to contamination events, hydrothermal alteration, and other processes; and we can use this information to better understand groundwater flow direction. The project has compiled a large amount of precipitation, soil, and groundwater chemistry data in the three focus areas distributed across in the State of Hawaii. Statistical analyses of these data sets will be performed in an effort to determine what is "normal" and what is anomalous chemistry for a given area. Where possible, results will be used to trace groundwater flow paths. Methods and preliminary results will be presented.

Coupling aerosol surface and bulk chemistry with a kinetic double layer model (K2-SUB: oxidation of oleic acid by ozone

Directory of Open Access Journals (Sweden)

C. Pfrang

2010-05-01

Full Text Available We present a kinetic double layer model coupling aerosol surface and bulk chemistry (K2-SUB based on the PRA framework of gas-particle interactions (Pöschl-Rudich-Ammann, 2007. K2-SUB is applied to a popular model system of atmospheric heterogeneous chemistry: the interaction of ozone with oleic acid. We show that our modelling approach allows de-convoluting surface and bulk processes, which has been a controversial topic and remains an important challenge for the understanding and description of atmospheric aerosol transformation. In particular, we demonstrate how a detailed treatment of adsorption and reaction at the surface can be coupled to a description of bulk reaction and transport that is consistent with traditional resistor model formulations.

From literature data we have derived a consistent set of kinetic parameters that characterise mass transport and chemical reaction of ozone at the surface and in the bulk of oleic acid droplets. Due to the wide range of rate coefficients reported from different experimental studies, the exact proportions between surface and bulk reaction rates remain uncertain. Nevertheless, the model results suggest an important role of chemical reaction in the bulk and an approximate upper limit of ~10⁻¹¹ cm² s⁻¹ for the surface reaction rate coefficient. Sensitivity studies show that the surface accommodation coefficient of the gas-phase reactant has a strong non-linear influence on both surface and bulk chemical reactions. We suggest that K2-SUB may be used to design, interpret and analyse future experiments for better discrimination between surface and bulk processes in the oleic acid-ozone system as well as in other heterogeneous reaction systems of atmospheric relevance.

The concept, reality and utility of single-site heterogeneous catalysts (SSHCs).

Science.gov (United States)

Thomas, John Meurig

2014-05-07

Very substantial advances have recently been made in the design and construction of solid catalysts and in elucidating both their mode of operation and the factors that determine their selectivity and longevity. This Perspective explains how and why such progress has been made. One important factor, the deployment of single-site heterogeneous and enzymatic catalysts, used either alone or in conjunction with other strategies, including metabolic engineering, enables a multitude of new products (for example, environmentally clean jet fuel) to be readily manufactured. In a practical sense SSHCs enable the advantages of homogeneous and to a lesser degree enzymatic catalysts to be united with those of heterogeneous ones. With the aid of the vastly increasing families of nanoporous solids, desired catalytically active sites may be engineered in atomic detail on their inner, accessible surfaces, thereby opening up new possibilities in synthetic organic chemistry - as in the smooth formation of C-C and C[double bond, length as m-dash]N bonds in a number of intermolecular reactions - as well as in photocatalysts and in fluidized catalytic cracking of hydrocarbons.

Dynamic behavior of homogeneous and heterogeneous LMFBR core-design concepts

International Nuclear Information System (INIS)

Chang, Y.I.; Henryson, H. II; Orechwa, Y.; Su, S.F.; Greenman, G.; Blomquist, R.

1981-01-01

The emphasis is placed on obtaining an understanding of the inherent difference between homogeneous and heterogeneous core configurations regarding neutronic characteristics related to the dynamic behavior. The space-time neutronic and thermal-hydraulic behavior was analyzed in detail for various core configurations by using the FX2-TH, a two-dimensional kinetics code with thermal-hydraulic feedback. In addition, the relationship between the flux tilt and the fundamental-to-first harmonic eigenvalue separation, and the sodium void reactivity in heterogeneous cores were also sutdied

Playing and understanding chemistry: Reinterpreting a traditional game for educational use

Directory of Open Access Journals (Sweden)

Ana Carolina Rosa da Silva

2017-12-01

Full Text Available The importance of using educational games in the school context cannot be denied. Therefore, this article describes a study about the contributions of a game for teaching colligative properties. The game was used with a second-year class in a high school located in southeast Piauí, Brazil. It is a qualitative study; it used questionnaires for data collection and direct observation about phenomenological aspects that emerged during the application of the game. The results showed that the use of educational games is not common for the subjects observed. Their views on that use lead us to infer that the proposed playful activity has contributed to strengthen distinct aspects needed to improve the teaching and learning process in Chemistry

Heterogeneity maintenance in glioblastoma: a social network.

Science.gov (United States)

Bonavia, Rudy; Inda, Maria-del-Mar; Cavenee, Webster K; Furnari, Frank B

2011-06-15

Glioblastoma multiforme (GBM), the most common intracranial tumor in adults, is characterized by extensive heterogeneity at the cellular and molecular levels. This insidious feature arises inevitably in almost all cancers and has great significance for the general outcome of the malignancy, because it confounds our understanding of the disease and also intrinsically contributes to the tumor's aggressiveness and poses an obstacle to the design of effective therapies. The classic view that heterogeneity arises as the result of a tumor's "genetic chaos" and the more contemporary cancer stem cell (CSC) hypothesis tend to identify a single cell population as the therapeutic target: the prevailing clone over time in the first case and the CSC in the latter. However, there is growing evidence that the different tumor cell populations may not be simple bystanders. Rather, they can establish a complex network of interactions between each other and with the tumor microenvironment that eventually strengthens tumor growth and increases chances to escape therapy. These differing but complementary ideas about the origin and maintenance of tumor heterogeneity and its importance in GBM are reviewed here.

Application of Chemistry in Materials Research at NASA GRC

Science.gov (United States)

Kavandi, Janet L.

2016-01-01

Overview of NASA GRC Materials Development. New materials enabled by new chemistries offering unique properties and chemical processing techniques. Durability of materials in harsh environments requires understanding and modeling of chemical interaction of materials with the environment.

EPRI PWR primary water chemistry guidelines revision

International Nuclear Information System (INIS)

McElrath, Joel; Fruzzetti, Keith

2014-01-01

EPRI periodically updates the PWR Primary Water Chemistry Guidelines as new information becomes available and as required by NEI 97-06 (Steam Generator Program Guidelines) and NEI 03-08 (Guideline for the Management of Materials Issues). The last revision of the PWR water chemistry guidelines identified an optimum primary water chemistry program based on then-current understanding of research and field information. This new revision provides further details with regard to primary water stress corrosion cracking (PWSCC), fuel integrity, and shutdown dose rates. A committee of industry experts, including utility specialists, nuclear steam supply system (NSSS) and fuel vendor representatives, Institute of Nuclear Power Operations (INPO) representatives, consultants, and EPRI staff collaborated in reviewing the available data on primary water chemistry, reactor water coolant system materials issues, fuel integrity and performance issues, and radiation dose rate issues. From the data, the committee updated the water chemistry guidelines that all PWR nuclear plants should adopt. The committee revised guidance with regard to optimization to reflect industry experience gained since the publication of Revision 6. Among the changes, the technical information regarding the impact of zinc injection on PWSCC initiation and dose rate reduction has been updated to reflect the current level of knowledge within the industry. Similarly, industry experience with elevated lithium concentrations with regard to fuel performance and radiation dose rates has been updated to reflect data collected to date. Recognizing that each nuclear plant owner has a unique set of design, operating, and corporate concerns, the guidelines committee has retained a method for plant-specific optimization. Revision 7 of the Pressurized Water Reactor Primary Water Chemistry Guidelines provides guidance for PWR primary systems of all manufacture and design. The guidelines continue to emphasize plant

Non-thermally activated chemistry

International Nuclear Information System (INIS)

Stiller, W.

1987-01-01

The subject is covered under the following headings: state-of-the art of non-thermally activated chemical processes; basic phenomena in non-thermal chemistry including mechanochemistry, photochemistry, laser chemistry, electrochemistry, photo-electro chemistry, high-field chemistry, magneto chemistry, plasma chemistry, radiation chemistry, hot-atom chemistry, and positronium and muonium chemistry; elementary processes in non-thermal chemistry including nuclear chemistry, interactions of electromagnetic radiations, electrons and heavy particles with matter, ionic elementary processes, elementary processes with excited species, radicalic elementary processes, and energy-induced elementary processes on surfaces and interfaces; and comparative considerations. An appendix with historical data and a subject index is given. 44 figs., 41 tabs., and 544 refs

Control and Characterization of Titanium Dioxide Morphology: Applications in Surface Organometallic Chemistry

KAUST Repository

Jeantelot, Gabriel

2014-05-01

Surface Organometallic Chemistry leads to the combination of the high activity and specificity of homogeneous catalysts with the recoverability and practicality of heterogeneous catalysts. Most metal complexes used in this chemistry are grafted on metal oxide supports such as amorphous silica (SiO2) and γ-alumina (Al2O3). In this thesis, we sought to enable the use of titania (TiO2) as a new support for single-site well-defined grafting of metal complexes. This was achieved by synthesizing a special type of anatase-TiO2, bearing a high density of identical hydroxyl groups, through hydrothermal synthesis then post-treatment under high vacuum followed by oxygen flow, and characterized by several analytical techniques including X-ray diffraction, transmission electron microscopy, infrared spectroscopy and nuclear magnetic resonance. Finally, as a proof of concept, the grafting of vanadium oxychloride (VOCl3) was successfully attempted.

Heterogeneity and subjectivity in binary-state opinion formation systems

International Nuclear Information System (INIS)

Guo, Long; Luo, Zhongjie; Zhu, Yueying

2013-01-01

In society, there is heterogeneous interaction and randomness in human decision making. In order to unfold the roles and the competition of the two factors mentioned above in opinion formation, we propose a toy model, which follows a majority rule with a Fermi function, on scale-free networks with degree exponent γ. The heterogeneous interaction is related to the connectivity of a person with the interactive parameter β, and the randomness of human decision making is quantified by the interaction noise T. We find that a system with heterogeneity of network topology and interaction shows robustness perturbed by the interaction noise T according to the theoretical analysis and numerical simulation. Then, when T → 0, the homogeneous interaction (β ≃ 0) has a powerful implication for the emergence of a consensus state. Furthermore, the emergence of the two extreme values shows the competition of the heterogeneity of interaction and the subjectivity of human decision making in opinion formation. Our present work provides some perspective on and tools for understanding the diversity of opinion in our society. (paper)

Foreign-Language Study Still Required for Chemistry.

Science.gov (United States)

Chemical and Engineering News, 1983

1983-01-01

Results of a survey of schools granting American Chemical Society-approved degrees indicate that most chemistry departments still require graduate students to understand a foreign language, despite much discussion in the past few years that the requirement might be outdated or that competency with computers is more relevant to chemists. (Author/JN)

Chemistry Vocabulary Attainment among Higher Secondary Students

Science.gov (United States)

Gafoor, K. Abdul; Greeshma, K.

2014-01-01

In the context of growing empirical evidence to lack of clear understanding of the language of the science content, undesirable student outcomes including difficulty in learning science and a lack of interest with their science content area, and chemistry being particularly loaded with specialized terminology of its own, this study analyzed the…

Heterogeneous nucleation of calcium oxalate on native oxide surfaces

International Nuclear Information System (INIS)

Song, L.; Pattillo, M.J.; Graff, G.L.; Campbell, A.A.; Bunker, B.C.

1994-04-01

The aqueous deposition of calcium oxalate onto colloidal oxides has been studied as a model system for understanding heterogeneous nucleation processes of importance in biomimetic synthesis of ceramic thin films. Calcium oxalate nucleation has been monitored by measuring induction times for nucleation using Constant Composition techniques and by measuring nucleation densities on extended oxide surfaces using an atomic force microscope. Results show that the dependence of calcium oxalate nucleation on solution supersaturation fits the functional form predicted by classical nucleation theories. Anionic surfaces appear to promote nucleation better than cationic surfaces, lowering the effective energy barrier to heterogeneous nucleation

Using Think-Aloud Protocols to Investigate Secondary School Chemistry Teachers' Misconceptions about Chemical Equilibrium

Science.gov (United States)

Cheung, Derek

2009-01-01

Secondary school chemistry teachers' understanding of chemical equilibrium was investigated through interviews using the think-aloud technique. The interviews were conducted with twelve volunteer chemistry teachers in Hong Kong. Their teaching experience ranged from 3 to 18 years. They were asked to predict what would happen to the equilibrium…

Nitric oxide reduction in coal combustion: role of char surface complexes in heterogeneous reactions

Energy Technology Data Exchange (ETDEWEB)

Arenillas, A.; Rubiera, F.; Pis, J.J. [Instituto Nacional del Carbon, CSIC, Oviedo (Spain)

2002-12-15

Nitrogen oxides are one of the major environmental problems arising from fossil fuel combustion. Coal char is relatively rich in nitrogen, and so this is an important source of nitrogen oxides during coal combustion. However, due to its carbonaceous nature, char can also reduce NO through heterogeneous reduction. The objectives of this work were on one hand to compare NO emissions from coal combustion in two different types of equipment and on the other hand to study the influence of char surface chemistry on NO reduction. A series of combustion tests were carried out in two different scale devices: a thermogravimetric analyzer coupled to a mass spectrometer and an FTIR (TG-MS-FTIR) and a fluidized bed reactor with on-line battery of analyzers. According to the results obtained, it can be said that the TG-MS-FTIR system provides valuable information about NO heterogeneous reduction and it can give good trends of the behaviour in other combustion equipments, i.e. fluidized bed combustors. It has been also pointed out that NO-char interaction depends to a large extent on temperature. In the low-temperature range NO heterogeneous reduction seems to be controlled by the evolution of surface complexes. In the high-temperature range a different mechanism is involved in NO heterogeneous reduction, the nature of the carbon matrix being a key factor. 27 refs., 6 figs., 1 tab.

Thermal inertia and surface heterogeneity on Mars

Science.gov (United States)

Putzig, Nathaniel E.

Thermal inertia derived from temperature observations is critical for understanding surface geology and assessing potential landing sites on Mars. Derivation methods generally assume uniform surface properties for any given observation. Consequently, horizontal heterogeneity and near-surface layering may yield apparent thermal inertia that varies with time of day and season. To evaluate the effects of horizontal heterogeneity, I modeled the thermal behavior of surfaces containing idealized material mixtures (dust, sand, duricrust, and rocks) and differing slope facets. These surfaces exhibit diurnal and seasonal variability in apparent thermal inertia of several 100 tiu, 1 even for components with moderately contrasting thermal properties. To isolate surface effects on the derived thermal inertia of Mars, I mapped inter- annual and seasonal changes in albedo and atmospheric dust opacity, accounting for their effects in a modified derivation algorithm. Global analysis of three Mars years of MGS-TES 2 data reveals diurnal and seasonal variations of ~200 tiu in the mid-latitudes and 600 tiu or greater in the polar regions. Correlation of TES results and modeled apparent thermal inertia of heterogeneous surfaces indicates pervasive surface heterogeneity on Mars. At TES resolution, the near-surface thermal response is broadly dominated by layering and is consistent with the presence of duricrusts over fines in the mid-latitudes and dry soils over ground ice in the polar regions. Horizontal surface mixtures also play a role and may dominate at higher resolution. In general, thermal inertia obtained from single observations or annually averaged maps may misrepresent surface properties. In lieu of a robust heterogeneous- surface derivation technique, repeat coverage can be used together with forward-modeling results to constrain the near-surface heterogeneity of Mars. 1 tiu == J m -2 K -1 s - 2 Mars Global Surveyor Thermal Emission Spectrometer

Green chemistry: A tool in Pharmaceutical Chemistry

OpenAIRE

Smita Talaviya; Falguni Majumdar

2012-01-01

Green chemistry expresses an area of research developing from scientific discoveries about pollution awareness and it utilizes a set of principles that reduces or eliminates the use or generation of hazardous substances in all steps of particular synthesis or process. Chemists and medicinal scientists can greatly reduce the risk to human health and the environment by following all the valuable principles of green chemistry. The most simple and direct way to apply green chemistry in pharmaceut...

Atmospheric Chemistry of Micrometeoritic Organic Compounds

Science.gov (United States)

Kress, M. E.; Belle, C. L.; Pevyhouse, A. R.; Iraci, L. T.

2011-01-01

Micrometeorites approx.100 m in diameter deliver most of the Earth s annual accumulation of extraterrestrial material. These small particles are so strongly heated upon atmospheric entry that most of their volatile content is vaporized. Here we present preliminary results from two sets of experiments to investigate the fate of the organic fraction of micrometeorites. In the first set of experiments, 300 m particles of a CM carbonaceous chondrite were subject to flash pyrolysis, simulating atmospheric entry. In addition to CO and CO2, many organic compounds were released, including functionalized benzenes, hydrocarbons, and small polycyclic aromatic hydrocarbons. In the second set of experiments, we subjected two of these compounds to conditions that simulate the heterogeneous chemistry of Earth s upper atmosphere. We find evidence that meteor-derived compounds can follow reaction pathways leading to the formation of more complex organic compounds.

Mass Spectrometry Imaging for the Investigation of Intratumor Heterogeneity.

Science.gov (United States)

Balluff, B; Hanselmann, M; Heeren, R M A

2017-01-01

One of the big clinical challenges in the treatment of cancer is the different behavior of cancer patients under guideline therapy. An important determinant for this phenomenon has been identified as inter- and intratumor heterogeneity. While intertumor heterogeneity refers to the differences in cancer characteristics between patients, intratumor heterogeneity refers to the clonal and nongenetic molecular diversity within a patient. The deciphering of intratumor heterogeneity is recognized as key to the development of novel therapeutics or treatment regimens. The investigation of intratumor heterogeneity is challenging since it requires an untargeted molecular analysis technique that accounts for the spatial and temporal dynamics of the tumor. So far, next-generation sequencing has contributed most to the understanding of clonal evolution within a cancer patient. However, it falls short in accounting for the spatial dimension. Mass spectrometry imaging (MSI) is a powerful tool for the untargeted but spatially resolved molecular analysis of biological tissues such as solid tumors. As it provides multidimensional datasets by the parallel acquisition of hundreds of mass channels, multivariate data analysis methods can be applied for the automated annotation of tissues. Moreover, it integrates the histology of the sample, which enables studying the molecular information in a histopathological context. This chapter will illustrate how MSI in combination with statistical methods and histology has been used for the description and discovery of intratumor heterogeneity in different cancers. This will give evidence that MSI constitutes a unique tool for the investigation of intratumor heterogeneity, and could hence become a key technology in cancer research. © 2017 Elsevier Inc. All rights reserved.

An ideal teaching program of nuclear chemistry in the undergraduate chemistry curriculum

International Nuclear Information System (INIS)

Uenak, T.

2009-01-01

It is well known that several reports on the common educational problems of nuclear chemistry have been prepared by certain groups of experts from time to time. According to very important statements in these reports, nuclear chemistry and related courses generally do not take sufficient importance in undergraduate chemistry curricula and it was generally proposed that nuclear chemistry and related courses should be introduced into undergraduate chemistry curricula at universities worldwide. Starting from these statements, an ideal program in an undergraduate chemistry curriculum was proposed to be introduced into the undergraduate chemistry program at the Department of Chemistry, Ege University, in Izmir, Turkey during the regular updating of the chemistry curriculum. Thus, it has been believed that this Department of Chemistry has recently gained an ideal teaching program in the field of nuclear chemistry and its applications in scientific, industrial, and medical sectors. In this contribution, the details of this program will be discussed. (author)

Towards Eco-reflexive Science Education. A Critical Reflection About Educational Implications of Green Chemistry

Science.gov (United States)

Sjöström, Jesper; Eilks, Ingo; Zuin, Vânia G.

2016-05-01

The modern world can be described as a globalized risk society. It is characterized by increasing complexity, unpredictable consequences of techno-scientific innovations and production, and its environmental consequences. Therefore, chemistry, just like many other knowledge areas, is in an ongoing process of environmentalization. For example, green chemistry has emerged as a new chemical metadiscipline and movement. The philosophy of green chemistry was originally based on a suggestion of twelve principles for environment-friendly chemistry research and production. The present article problematizes limitations in green chemistry when it comes to education. It argues that the philosophy of green chemistry in the context of education needs to be extended with socio-critical perspectives to form educated professionals and citizens who are able to understand the complexity of the world, to make value-based decisions, and to become able to engage more thoroughly in democratic decision-making on sustainability issues. Different versions of sustainability-oriented science/chemistry education are discussed to sharpen a focus on the most complex type, which is Bildung-oriented, focusing emancipation and leading to eco-reflexive education. The term eco- reflexive is used for a problematizing stance towards the modern risk society, an understanding of the complexity of life and society and their interactions, and a responsibility for individual and collective actions towards socio-ecojustice and global sustainability. The philosophical foundation and characteristics of eco-reflexive science education are sketched on in the article.

Visual Analytics for Heterogeneous Geoscience Data

Science.gov (United States)

Pan, Y.; Yu, L.; Zhu, F.; Rilee, M. L.; Kuo, K. S.; Jiang, H.; Yu, H.

2017-12-01

Geoscience data obtained from diverse sources have been routinely leveraged by scientists to study various phenomena. The principal data sources include observations and model simulation outputs. These data are characterized by spatiotemporal heterogeneity originated from different instrument design specifications and/or computational model requirements used in data generation processes. Such inherent heterogeneity poses several challenges in exploring and analyzing geoscience data. First, scientists often wish to identify features or patterns co-located among multiple data sources to derive and validate certain hypotheses. Heterogeneous data make it a tedious task to search such features in dissimilar datasets. Second, features of geoscience data are typically multivariate. It is challenging to tackle the high dimensionality of geoscience data and explore the relations among multiple variables in a scalable fashion. Third, there is a lack of transparency in traditional automated approaches, such as feature detection or clustering, in that scientists cannot intuitively interact with their analysis processes and interpret results. To address these issues, we present a new scalable approach that can assist scientists in analyzing voluminous and diverse geoscience data. We expose a high-level query interface that allows users to easily express their customized queries to search features of interest across multiple heterogeneous datasets. For identified features, we develop a visualization interface that enables interactive exploration and analytics in a linked-view manner. Specific visualization techniques such as scatter plots to parallel coordinates are employed in each view to allow users to explore various aspects of features. Different views are linked and refreshed according to user interactions in any individual view. In such a manner, a user can interactively and iteratively gain understanding into the data through a variety of visual analytics operations. We

Dynamical Systems Approach to Endothelial Heterogeneity

Science.gov (United States)

Regan, Erzsébet Ravasz; Aird, William C.

2012-01-01

Rationale Objective Here we reexamine our current understanding of the molecular basis of endothelial heterogeneity. We introduce multistability as a new explanatory framework in vascular biology. Methods We draw on the field of non-linear dynamics to propose a dynamical systems framework for modeling multistability and its derivative properties, including robustness, memory, and plasticity. Conclusions Our perspective allows for both a conceptual and quantitative description of system-level features of endothelial regulation. PMID:22723222

Representational Classroom Practices that Contribute to Students' Conceptual and Representational Understanding of Chemical Bonding

Science.gov (United States)

Hilton, Annette; Nichols, Kim

2011-11-01

Understanding bonding is fundamental to success in chemistry. A number of alternative conceptions related to chemical bonding have been reported in the literature. Research suggests that many alternative conceptions held by chemistry students result from previous teaching; if teachers are explicit in the use of representations and explain their content-specific forms and functions, this might be avoided. The development of an understanding of and ability to use multiple representations is crucial to students' understanding of chemical bonding. This paper draws on data from a larger study involving two Year 11 chemistry classes (n = 27, n = 22). It explores the contribution of explicit instruction about multiple representations to students' understanding and representation of chemical bonding. The instructional strategies were documented using audio-recordings and the teacher-researcher's reflection journal. Pre-test-post-test comparisons showed an improvement in conceptual understanding and representational competence. Analysis of the students' texts provided further evidence of the students' ability to use multiple representations to explain macroscopic phenomena on the molecular level. The findings suggest that explicit instruction about representational form and function contributes to the enhancement of representational competence and conceptual understanding of bonding in chemistry. However, the scaffolding strategies employed by the teacher play an important role in the learning process. This research has implications for professional development enhancing teachers' approaches to these aspects of instruction around chemical bonding.

Non-equilibrium chemistry in the solar nebula and early solar system: Implications for the chemistry of comets

Science.gov (United States)

Fegley, Bruce, Jr.

1989-01-01

Theoretical models of solar nebula and early solar system chemistry which take into account the interplay between chemical, physical, and dynamical processes have great utility for deciphering the origin and evolution of the abundant chemically reactive volatiles (H, O, C, N, S) observed in comets. In particular, such models are essential for attempting to distinguish between presolar and solar nebula products and for quantifying the nature and duration of nebular and early solar system processing to which the volatile constituents of comets have been subjected. The diverse processes and energy sources responsible for chemical processing in the solar nebula and early solar system are discussed. The processes considered include homogeneous and heterogeneous thermochemical and photochemical reactions, and disequilibration resulting from fluid transport, condensation, and cooling whenever they occur on timescales shorter than those for chemical reactions.

Evaluation of an educational program on deciphering heterogeneity for medical coverage decisions.

Science.gov (United States)

Warholak, Terri L; Hilgaertner, Jianhua W; Dean, Joni L; Taylor, Ann M; Hines, Lisa E; Hurwitz, Jason; Brown, Mary; Malone, Daniel C

2014-06-01

It is increasingly important for decision makers, such as medical and pharmacy managers (or pharmacy therapeutics committee members and staff), to understand the variation and diversity in treatment response as decisions shift from an individual patient perspective to optimizing care for populations of patients. To assess the effectiveness of an instructional program on heterogeneity designed for medical and pharmacy managers. A live educational program was offered to members of the Academy of Managed Care Pharmacy at the fall 2012 educational meeting and also to medical directors and managers attending a national payer roundtable meeting in October 2012. Participants completed a retrospective pretest-posttest assessment of their knowledge, attitudes, and self-efficacy immediately following the program. Participants were offered the opportunity to participate in a follow-up assessment 6 months later. Willing participants for the follow-up assessment were contacted via e-mail and telephone. Rasch rating scale models were used to compare pre- and postscores measuring participants' knowledge about and attitude towards heterogeneity. A total of 49 individuals completed the retrospective pretest-posttest assessment and agreed to be a part of the program evaluation. Fifty percent (n = 25) of participants had heard of the phrase "heterogeneity of treatment effect," and 36 (72%) were familiar with the phrase "individualized treatment effect" prior to the live program. Participants reported a significant improvement in knowledge of heterogeneity (P  less than  0.01) and attitudes about heterogeneity (P  less than  0.01) immediately after attending the program. At the time of the educational program, participants had either never considered heterogeneity (26%) or reported not knowing (28%) whether their organizations considered it when determining basic coverage. Participants were more likely to report "sometimes" considering heterogeneity for determining

Joining Forces: The Chemical Biology-Medicinal Chemistry Continuum.

Science.gov (United States)

Plowright, Alleyn T; Ottmann, Christian; Arkin, Michelle; Auberson, Yves P; Timmerman, Henk; Waldmann, Herbert

2017-09-21

The scientific advances being made across all disciplines are creating ever-increasing opportunities to enhance our knowledge of biological systems and how they relate to human disease. One of the central driving forces in discovering new medicines is medicinal chemistry, where the design and synthesis of novel compounds has led to multiple drugs. Chemical biology, sitting at the interface of many disciplines, has now emerged as a major contributor to the understanding of biological systems and is becoming an integral part of drug discovery. Bringing chemistry and biology much closer and blurring the boundaries between disciplines is creating new opportunities to probe and understand biology; both disciplines play key roles and need to join forces and work together effectively to synergize their impact. The power of chemical biology will then reach its full potential and drive innovation, leading to the discovery of transformative medicines to treat patients. Advances in cancer biology and drug discovery highlight this potential. Copyright © 2017 Elsevier Ltd. All rights reserved.

BWR Water Chemistry Guidelines: 1993 Revision, Normal and hydrogen water chemistry

International Nuclear Information System (INIS)

Karlberg, G.; Goddard, C.; Fitzpatrick, S.

1994-02-01

The goal of water chemistry control is to extend the operating life of the reactor and rector coolant system, balance-of-plant components, and turbines while simultaneously controlling costs to safeguard the continued economic viability of the nuclear power generation investment. To further this goal an industry committee of chemistry personnel prepared guidelines to identify the benefits, risks, and costs associated with water chemistry in BWRs and to provide a template for an optimized water chemistry program. This document replaces the BWR Normal Water Chemistry Guidelines - 1986 Revision and the BWR Hydrogen Water Chemistry Guidelines -- 1987 Revision. It expands on the previous guidelines documents by covering the economic implications of BWR water chemistry control

Grain surface chemistry in protoplanetary disks

International Nuclear Information System (INIS)

Reboussin, Laura

2015-01-01

Planetary formation occurs in the protoplanetary disks of gas and dust. Although dust represents only 1% of the total disk mass, it plays a fundamental role in disk chemical evolution since it acts as a catalyst for the formation of molecules. Understanding this chemistry is therefore essential to determine the initial conditions from which planets form. During my thesis, I studied grain-surface chemistry and its impact on the chemical evolution of molecular cloud, initial condition for disk formation, and protoplanetary disk. Thanks to numerical simulations, using the gas-grain code Nautilus, I showed the importance of diffusion reactions and gas-grain interactions for the abundances of gas-phase species. Model results combined with observations also showed the effects of the physical structure (in temperature, density, AV) on the molecular distribution in disks. (author)

The Complex Chemistry of Embedded Protostars

DEFF Research Database (Denmark)

Lykke, Julie Maria

- or molecular astrophysics - has evolved fast in recent years, due to major technological advancements for radio telescopes. But some of the most central questions still remain unanswered: how, where and when are complex organic molecules formed around young stars? How complex can these molecules become......? Is there a difference in the chemistry for high- and low-mass protostars? The work in this thesis aim to provide answer for these questions by searching for molecules where they have not been detected before and by comparing the relative abundance of different molecules to models and laboratory work as well as between......- and low-mass sources. Modified models and laboratory work as well as more observations are therefore needed to further develop our understanding of the chemistry occurring in star-forming regions....

Understanding flood-induced water chemistry variability extracting temporal patterns with the LDA method

Science.gov (United States)

Aubert, A. H.; Tavenard, R.; Emonet, R.; De Lavenne, A.; Malinowski, S.; Guyet, T.; Quiniou, R.; Odobez, J.; Merot, P.; Gascuel-odoux, C.

2013-12-01

Studying floods has been a major issue in hydrological research for years, both in quantitative and qualitative hydrology. Stream chemistry is a mix of solutes, often used as tracers, as they originate from various sources in the catchment and reach the stream by various flow pathways. Previous studies (for instance (1)) hypothesized that stream chemistry reaction to a rainfall event is not unique but varies seasonally, and according to the yearly meteorological conditions. Identifying a typology of flood temporal chemical patterns is a way to better understand catchment processes at the flood and seasonal time scale. We applied a probabilistic model (Latent Dirichlet Allocation or LDA (2)) mining recurrent sequential patterns from a dataset of floods. A set of 472 floods was automatically extracted from a daily 12-year long record of nitrate, dissolved organic carbon, sulfate and chloride concentrations. Rainfall, discharge, water table depth and temperature are also considered. Data comes from a long-term hydrological observatory (AgrHys, western France) located at Kervidy-Naizin. From each flood, a document has been generated that is made of a set of "hydrological words". Each hydrological word corresponds to a measurement: it is a triplet made of the considered variable, the time at which the measurement is made (relative to the beginning of the flood), and its magnitude (that can be low, medium or high). The documents and the number of pattern to be mined are used as input data to the LDA algorithm. LDA relies on spotting co-occurrences (as an alternative to the more traditional study of correlation) between words that appear within the flood documents. It has two nice properties that are its ability to easily deal with missing data and its additive property that allows a document to be seen as a mixture of several flood patterns. The output of LDA is a set of patterns easily represented in graphics. These patterns correspond to typical reactions to rainfall

Chemistry-Nuclear Chemistry Division. Progress report, October 1980-September 1981

International Nuclear Information System (INIS)

Ryan, R.R.

1982-05-01

This report describes major progress in the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory during FY 1981. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, medical radioisotopes research, element migration and fixation, nuclear waste isolation research, inorganic and structural chemistry, isotope separation, analysis and applications, the newly established Nuclear Magnetic Resonance Center, atomic and molecular collisions, molecular spectroscopy, nuclear cosmochemistry, nuclear structure and reactions, pion charge exchange, radiochemical separations, theoretical chemistry, and unclassified weapons research

Chemistry-Nuclear Chemistry Division. Progress report, October 1980-September 1981

Energy Technology Data Exchange (ETDEWEB)

Ryan, R.R. (comp.)

1982-05-01

This report describes major progress in the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory during FY 1981. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, medical radioisotopes research, element migration and fixation, nuclear waste isolation research, inorganic and structural chemistry, isotope separation, analysis and applications, the newly established Nuclear Magnetic Resonance Center, atomic and molecular collisions, molecular spectroscopy, nuclear cosmochemistry, nuclear structure and reactions, pion charge exchange, radiochemical separations, theoretical chemistry, and unclassified weapons research.

Complex chemistry of Np(V) in aqueous solutions

International Nuclear Information System (INIS)

Inoue, Yasushi

1989-01-01

Despite the importance of Np(V) in both the nuclear chemical engineering and the actinoid chemistry, little work has been performed on the complex chemistry of Np(V) in aqueous solutions, since Np(V) reacts less readily with various ligands. The author has directed his effort to understand the chemical behavior of Np(V) in aqueous solutions, especially the determination of the stability constants of Np(V) complexes with various ligands. A part of the results obtained so far is presented in the following order. (1) The synergistic extraction of Np(V) as a method for studying the complex chemistry of Np(V): TTA-MTOA(methyltrioctylammonium chloride), TTA-phen and TTA-TOPO. (2) The determination of the stability constants of Np(V) complexes with 22 organic- and 5 inorganic ligands by means of the solvent extraction. (3) The distribution of the chemical species of Np(V) in solutions under various conditions

Electrolytes and interphasial chemistry in Li ion devices

Energy Technology Data Exchange (ETDEWEB)

Xu, K. [Electrochemistry Branch, Sensors and Electron Devices Directorate, U. S. Army Research Laboratory, Adelphi, Maryland, 20783-1197 (United States)

2010-07-01

Since its appearance in 1991, the Li ion battery has been the major power source driving the rapid digitalisation of our daily life; however, much of the processes and mechanisms underpinning this newest battery chemistry remains poorly understood. As in any electrochemical device, the major challenge comes from the electrolyte/electrode interfaces, where the discontinuity in charge distribution and extreme disequality in electric forces induce diversified processes that eventually determine the kinetics of Li{sup +} intercalation chemistry. This article will summarize the most recent efforts on the fundamental understanding of the interphases in Li ion devices. Emphasis will be placed on the formation chemistry of the so-called 'SEI' on graphitic anode, the effect of solvation sheath structure of Li{sup +} on the intercalation energy barrier, and the feasibility of tailoring a desired interphase. Biologically inspired approaches to an ideal interphase will also be briefly discussed. (author)

Chemistry and Star Formation: A Love-Hate Relationship

Science.gov (United States)

Jiménez-Serra, Izaskun; Zhang, Qizhou; Patel, Nimesh; Lu, Xing; Wang, Ke; Testi, Leonardo; Caselli, Paola; Martin-Pintado, Jesus

2014-06-01

The development of the broad bandwidth receivers at the Submillimeter Array (SMA) a decade ago opened up the possibility to observe tens of molecular lines at high angular resolution simultaneously. The unprecedented wealth of molecular line data provided by the SMA allowed for the first time detailed studies of the chemistry in star-forming regions. These studies have revealed that chemistry is a useful tool to pin down the internal physical structure and the physical processes involved in the process of low-mass and high-mass star formation. In this talk, I will review the most important advances in our understanding of the star-formation process through chemistry thanks to the SMA, and I will present the challenges that will be faced in the next decade in this field of research thanks to the advent of new instrumentation such as the Atacama Large Millimeter/Submillimeter Array and the Square Kilometer Array.

Electrolytes and Interphasial Chemistry in Li Ion Devices

Directory of Open Access Journals (Sweden)

Kang Xu

2010-01-01

Full Text Available Since its appearance in 1991, the Li ion battery has been the major power source driving the rapid digitalization of our daily life; however, much of the processes and mechanisms underpinning this newest battery chemistry remains poorly understood. As in any electrochemical device, the major challenge comes from the electrolyte/electrode interfaces, where the discontinuity in charge distribution and extreme disequality in electric forces induce diversified processes that eventually determine the kinetics of Li+ intercalation chemistry. This article will summarize the most recent efforts on the fundamental understanding of the interphases in Li ion devices. Emphasis will be placed on the formation chemistry of the so-called “SEI” on graphitic anode, the effect of solvation sheath structure of Li+ on the intercalation energy barrier, and the feasibility of tailoring a desired interphase. Biologically inspired approaches to an ideal interphase will also be briefly discussed.

Assessment of heterogeneous geological environment using geostatistical techniques

International Nuclear Information System (INIS)

Toida, Masaru; Suyama, Yasuhiro; Shiogama, Yukihiro; Atsumi, Hiroyuki; Abe, Yasunori; Furuichi, Mitsuaki

2003-02-01

'Geoscientific' research at Tono are developing site investigation and assessment techniques in geological environment. One of their important themes is to establish rational methodology to reduce uncertainties associated with the understanding of geological environment, which often exhibits significant heterogeneity. Purpose of this study is to identify and evaluate uncertainties associated with the understanding of geological environment. Because it is useful to guide designing effective site investigation techniques to reduce the uncertainty. For this, a methodology of the uncertainty analysis concerning the heterogeneous geological environment has been developed. In this report the methodology has also been tested through an exercise attempted in Tono area to demonstrate its applicability. This report summarizes as follows: 1) The exercise shows that the methodology considered 'variability' and 'ignorance' can demonstrate its applicability at three-dimensional case. 2) The exercise shows that the methodology can identity and evaluate uncertainties concerning ground water flow associated with performance assessment. 3) Based on sensitivity analyses, it is possible for the methodology to support designs of the following stage investigations to reduce the uncertainties efficiently. (author)

ANT International chemistry update and best practices

International Nuclear Information System (INIS)

Nordmann, F.; Odar, S.; Venz, H.; Kysela, J.; Ruehle, W.; Riess, R.

2010-01-01

There is an increasing number of Nuclear Power Plants (NPP) in various countries. Their chemistry practices are different due to the variety of designs and experiences while in the past the view was more monolithic. This is allowing a very rich experience that is extremely difficult to fully be aware of. ANT International is now collecting and evaluating these data as well as related R and D Information. This allows interested parties to have an easier access to the various sources of information. The chemistry experts associated to ANT International have been gathering a comprehensive detailed view of: The numerous laboratory data gained all over the world during the past decades; The extensive plant operating experiences with various types of chemistry strategies, crosschecked for various types of reactors designs and materials; An experienced international knowledge able to give the comprehensive overview that young engineers now in charge of many other activities are unable to fully cover. This paper gives the core conclusions of the detailed ANT International reports and results that have recently been gathered in the area of chemistry. It particularly covers: The primary water chemistry and its relation with radionuclides, dose rates and fuel behaviour; The secondary water chemistry focusing on its rationale selection depending on materials, design and other constraints; The start up and shutdown chemistry with it large variety of practices hardly understandable even for some experts; and, The maintenance remedies such as decontamination, steam generator cleaning and its alternate options. Various types of Reactor designs (PWR, VVER, BWR, CANDU®) are considered. The different materials, for example the impact of steam generator tubing and its evolution on the secondary water chemistry rationale or on the radioactivity built-up in the primary coolant, are described. The ways to improve the plant operation with a long term reliability as well as the most

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

Directory of Open Access Journals (Sweden)

Ales Styskalik

2017-05-01

Full Text Available This review is devoted to non-hydrolytic sol-gel chemistry. During the last 25 years, non-hydrolytic sol-gel (NHSG techniques were found to be attractive and versatile methods for the preparation of oxide materials. Compared to conventional hydrolytic approaches, the NHSG route allows reaction control at the atomic scale resulting in homogeneous and well defined products. Due to these features and the ability to design specific materials, the products of NHSG reactions have been used in many fields of application. The aim of this review is to present an overview of NHSG research in recent years with an emphasis on the syntheses of mixed oxides, silicates and phosphates. The first part of the review highlights well known condensation reactions with some deeper insights into their mechanism and also presents novel condensation reactions established in NHSG chemistry in recent years. In the second section we discuss porosity control and novel compositions of selected materials. In the last part, the applications of NHSG derived materials as heterogeneous catalysts and supports, luminescent materials and electrode materials in Li-ion batteries are described.

Ecosystem services capacity across heterogeneous forest types: understanding the interactions and suggesting pathways for sustaining multiple ecosystem services.

Science.gov (United States)

Alamgir, Mohammed; Turton, Stephen M; Macgregor, Colin J; Pert, Petina L

2016-10-01

As ecosystem services supply from tropical forests is declining due to deforestation and forest degradation, much effort is essential to sustain ecosystem services supply from tropical forested landscapes, because tropical forests provide the largest flow of multiple ecosystem services among the terrestrial ecosystems. In order to sustain multiple ecosystem services, understanding ecosystem services capacity across heterogeneous forest types and identifying certain ecosystem services that could be managed to leverage positive effects across the wider bundle of ecosystem services are required. We sampled three forest types, tropical rainforests, sclerophyll forests, and rehabilitated plantation forests, over an area of 32,000m(2) from Wet Tropics bioregion, Australia, aiming to compare supply and evaluate interactions and patterns of eight ecosystem services (global climate regulation, air quality regulation, erosion regulation, nutrient regulation, cyclone protection, habitat provision, energy provision, and timber provision). On average, multiple ecosystem services were highest in the rainforests, lowest in sclerophyll forests, and intermediate in rehabilitated plantation forests. However, a wide variation was apparent among the plots across the three forest types. Global climate regulation service had a synergistic impact on the supply of multiple ecosystem services, while nutrient regulation service was found to have a trade-off impact. Considering multiple ecosystem services, most of the rehabilitated plantation forest plots shared the same ordination space with rainforest plots in the ordination analysis, indicating that rehabilitated plantation forests may supply certain ecosystem services nearly equivalent to rainforests. Two synergy groups and one trade-off group were identified. Apart from conserving rainforests and sclerophyll forests, our findings suggest two additional integrated pathways to sustain the supply of multiple ecosystem services from a

Control of water chemistry in operating reactors

International Nuclear Information System (INIS)

Riess, R.

1997-01-01

Water chemistry plays a major role in fuel cladding corrosion and hydriding. Although a full understanding of all mechanisms involved in cladding corrosion does not exist, controlling the water chemistry has achieved quite some progress in recent years. As an example, in PWRs the activity transport is controlled by operating the coolant under higher pH-values (i.e. the ''modified'' B/Li-Chemistry). On the other hand, the lithium concentration is limited to a maximum value of 2 ppm in order to avoid an acceleration of the fuel cladding corrosion. In BWR plants, for example, the industry has learned on how to limit the copper concentration in the feedwater in order to limit CILC (Copper Induced Localized Corrosion) on the fuel cladding. However, economic pressures are leading to more rigorous operating conditions in power reactors. Fuel burnups are to be increased, higher efficiencies are to be achieved, by running at higher temperatures, plant lifetimes are to be extended. In summary, this paper will describe the state of the art in controlling water chemistry in operating reactors and it will give an outlook on potential problems that will arise when going to more severe operating conditions. (author). 3 figs, 6 tabs

Control of water chemistry in operating reactors

Energy Technology Data Exchange (ETDEWEB)

Riess, R [Siemens AG Unternehmensbereich KWU, Erlangen (Germany)

1997-02-01

Water chemistry plays a major role in fuel cladding corrosion and hydriding. Although a full understanding of all mechanisms involved in cladding corrosion does not exist, controlling the water chemistry has achieved quite some progress in recent years. As an example, in PWRs the activity transport is controlled by operating the coolant under higher pH-values (i.e. the ``modified`` B/Li-Chemistry). On the other hand, the lithium concentration is limited to a maximum value of 2 ppm in order to avoid an acceleration of the fuel cladding corrosion. In BWR plants, for example, the industry has learned on how to limit the copper concentration in the feedwater in order to limit CILC (Copper Induced Localized Corrosion) on the fuel cladding. However, economic pressures are leading to more rigorous operating conditions in power reactors. Fuel burnups are to be increased, higher efficiencies are to be achieved, by running at higher temperatures, plant lifetimes are to be extended. In summary, this paper will describe the state of the art in controlling water chemistry in operating reactors and it will give an outlook on potential problems that will arise when going to more severe operating conditions. (author). 3 figs, 6 tabs.

Heterogeneous Uptake of HO2 Radicals onto Atmospheric Aerosols

Science.gov (United States)

George, I. J.; Matthews, P. S.; Brooks, B.; Goddard, A.; Whalley, L. K.; Baeza-Romero, M. T.; Heard, D. E.

2011-12-01

The hydroxyl (OH) and hydroperoxyl (HO2) radicals, together known as HOx, play a vital role in atmospheric chemistry by controlling the oxidative capacity of the troposphere. The atmospheric lifetime and concentrations of many trace reactive species, such as volatile organic compounds (VOCs), are determined by HOx radical levels. Therefore, the ability to accurately predict atmospheric HOx concentrations from a detailed knowledge of their sources and sinks is a very useful diagnostic tool to assess our current understanding of atmospheric chemistry. Several recent field studies have observed significantly lower concentrations of HO2 radicals than predicted using box models, where HO2 loss onto aerosols was suggested as a possible missing sink [1, 2]. However, the mechanism on HO2 uptake onto aerosols and its impact on ambient HOx levels are currently not well understood. To improve our understanding of this process, we have conducted laboratory experiments to measure HO2 uptake coefficients onto submicron aerosol particles. The FAGE (Fluorescence Assay by Gas Expansion) technique, a highly sensitive laser induced fluorescence based detection method, was used to monitor HO2 uptake kinetics onto aerosol particles in an aerosol flow tube. The application of the FAGE technique allowed for kinetic experiments to be performed under low HO2 concentrations, i.e. [HO2] atomizing dilute salt solutions or by homogeneous nucleation. HO2 uptake coefficients (γ) have been measured for single-component solid and aqueous inorganic salt and organic aerosol particles with a wide range of hygroscopicities. HO2 uptake coefficients on solid particles were below the detection limit (γ < 0.001), whereas on aqueous aerosols uptake coefficients were somewhat larger (γ = 0.001 - 0.008). HO2 uptake coefficients were highest on aerosols containing metal ions, such as Cu and Fe. Humidity and aerosol pH did not significantly impact the reactive HO2 uptake. Preliminary experiments have also

Clays as mineral dust aerosol: An integrated approach to studying climate, atmospheric chemistry, and biogeochemical effects of atmospheric clay minerals in an undergraduate research laboratory

Science.gov (United States)

Hatch, C. D.; Crane, C. C.; Harris, K. J.; Thompson, C. E.; Miles, M. K.; Weingold, R. M.; Bucuti, T.

2011-12-01

Entrained mineral dust aerosol accounts for 45% of the global annual atmospheric aerosol load and can have a significant influence on important environmental issues, including climate, atmospheric chemistry, cloud formation, biogeochemical processes, visibility, and human health. 70% of all mineral aerosol mass originating from Africa consists of layered aluminosilicates, including illite, kaolinite, and montmorillonite clays. Clay minerals are a largely neglected component of mineral aerosol, yet they have unique physiochemical properties, including a high reactive surface area, large cation exchange capacities, small particle sizes, and a relatively large capacity to take up adsorbed water, resulting in expansion of clay layers (and a larger reactive surface area for heterogeneous interactions) in some cases. An integrated laboratory research approach has been implemented at Hendrix College, a Primarily Undergraduate Institution, in which undergraduate students are involved in independent and interdisciplinary research projects that relate the chemical aging processes (heterogeneous chemistry) of clay minerals as a major component of mineral aerosol to their effects on climate (water adsorption), atmospheric chemistry (trace gas uptake), and biogeochemistry (iron dissolution and phytoplankton biomarker studies). Preliminary results and future directions will be reported.

Scientific Information Analysis of Chemistry Dissertations Using Thesaurus of Chemistry

Directory of Open Access Journals (Sweden)

Taghi Rajabi

2017-09-01

Full Text Available : Concept maps of chemistry can be obtained from thesaurus of chemistry. Analysis of information in the field of chemistry is done at graduate level, based on comparing and analyzing chemistry dissertations by using these maps. Therefore, the use of thesaurus for analyzing scientific information is recommended. Major advantage of using this method, is that it is possible to obtain a detailed map of all academic researches across all branches of science. The researches analysis results in chemical science can play a key role in developing strategic research policies, educational programming, linking universities to industries and postgraduate educational programming. This paper will first introduce the concept maps of chemistry. Then, emerging patterns from the concept maps of chemistry will be used to analyze the trend in the academic dissertations in chemistry, using the data collected and stored in our database at Iranian Research Institute for Information Science and Technology (IranDoc over the past 10 years (1998-2009.

To leave from social scenario: on heterogeneity and specifity of populism

Directory of Open Access Journals (Sweden)

Sebastián Barros

2009-12-01

Full Text Available This paper is part of a discussion on the specificity of populism. Taking Laclau’s theorerical framework as a starting point, we analise the importance of the concept of heterogeneity in his argument. Later on, we analise Rancière’s understanding of politics as conflict and conclude that the idea of heterogeneity is central to a definition of populism. In this sense, we argue that heterogenity is something which is moved from its natural place in the order of domination, and starts to be taken as a part in the definition of the commonness of the community. This would have three specific effects over the subsequent political articulations. The inclusion of a heterogeneity would demonstrate the inexistance of the community of equals, forcing the need for a new representation of that community, now incarnated in a subject that, in the name of the past tort, claims to represent the universal plenitude of the community. Finally, we analise interventions by Gramsci and Ortega y Gasset in relation to the irruption of heterogeneity.