Chemical dynamics

CHEMICAL EDUCATION is changing rapidly, not only because of the explosive growth of knowledge but also because the new knowledge has stimulated reformulation of working principles in the science. Undergraduate curricula and individual courses are in constant flux. Nowhere is the change and challenge greater than in freshman chemistry. Teachers of freshmen must meet the intellectual needs of students who have had more sophisticated and stimulating high school courses than those given a decade ago. At the same time, the freshman teacher must be aware of the constant modification of the more advanced courses in chemistry and other fields that his students will study later. Continuous reformulation of courses sometimes results in the inclusion of valuable new material at the expense of other equally valuable material. We believe that this has happened in some of the sophisticated courses in freshman chemistry. Structural chemistry often receives far greater emphasis than chemical dynamics. In 1965, the Westheimer Report (Chemistry: Opportunities and Needs, National Academy of Sciences, 1965) identified the three major fields of chemistry as structure, dynamics, and synthesis. We firmly believe that a balanced course in general chemistry should reflect the outlook of this report. The study of modern chemical synthesis is too demanding to be covered in depth in an introductory course. However, chemical dynamics -- the systematic study of reactions and reactivity -- can and should be studied at the freshman level. The study of changing chemical systems is the most fascinating part of the field for many students, and its early introduction forms a solid foundation for later study. This small volume is our attempt to answer the need. The book is intended for students who have had introductory stoichiometry, energetics, and structure at the level of a modern freshman textbook (for example, Basic Principles of Chemistry, by H. B. Gray and G. P. Haight, Jr., W. A. Benjamin, Inc., New York, 1961). Chemical Dynamics is designed to accompany approximately 20-25 lectures to be given as the concluding section of a freshman chemistry course. We have chosen topics for their fundamental importance in dynamics and then tried to develop a presentation suitable for freshman classes. Discussion of each topic is limited, because chemistry majors will inevitably return to all the subject matter in more advanced courses. We hope that the following ideas have been introduced with a firm conceptual basis and in enough detail for the student to apply them to chemical reality. 1. Thermodynamics and kinetics are two useful measures of reactivity. 2. Characteristic patterns of reactivity are systematically related to molecular geometry and electronic structure. 3. Reaction mechanisms are fascinating in their own right and indispensable for identification of significant problems in reaction rate theory. 4. The concepts underlying experiments with elementary reaction processes (molecular beams) are simple, even though the engineering of the experiments is complicated. 5. Application of theories of elementary reaction rates to most reactions (slow reactions, condensed media, etc.) provides enough challenge to satisfy the most ambitious young scientist. The book includes exercises at the end of each chapter except the last. Their purpose is didactic, inasmuch as most have been written with the aim of strengthening a particular point emphasized in the chapter, or of introducing an important topic which was not developed in the text for reasons of space and which would normally be taken up in greater detail in later courses. The material in this volume has been adapted primarily from a portion of the lectures given by H.B.G. and G.S.H. to the Chemistry 2 students at the California Institute of Technology during the academic years 1966-1967 and 1967-1968. These lectures were taped, written up by J.B.D., and distributed to the students in the form of class notes. The final manuscript was written after class-testing of the notes. Our decision to revise the Chemistry 2 notes in the form of an introductory text was made after H.B.G. and G.S.H. participated in the San Clemente Chemical Dynamics Conference, held in December 1966 under the sponsorship of the Advisory Council of College Chemistry. At San Clemente we found we were not the only group concerned over the exclusion of significant reference to chemical reactions and reactivity relationships in freshman courses. In addition to their general encouragement, which provided the necessary additional impetus, these colleagues prepared a series of papers for publication in an issue of the Journal of Chemical Education. It is a pleasure to acknowledge here the direct contribution these papers made in shaping the final form of our volume; specifically, in preparing Chapter 6, we have drawn examples from the San Clemente papers of Professors R. Marcus, A. Kuppermann and E. F. Greene, and J. Halpern. The concluding chapter of this book was developed from the lectures given by Professors E. F. Greene (dynamics in simple systems), Richard Wolfgang (atomic carbon), John D. Roberts (nuclear magnetic resonance), and F. C. Anson (electrochemical dynamics) to the students of Chemistry 2 in May 1967. These colleagues have kindly given us permission to use their material. We are grateful to Professors Ralph G. Pearson and Paul Haake, who read the entire manuscript and offered valuable criticism. It is a special pleasure to acknowledge the enormous contribution our students in Chemistry 2 made to the project. Their enthusiastic, critical attitude helped us make many improvements in the manuscript. Thanks are also due to four very special members of the staff of W. A. Benjamin, Inc., for seeing this project through with infectious vigor. Finally, and not the least, we acknowledge the role Susan Brittenham and Eileen McKoy played in preparing the final manuscript. JOSEPH B. DENCE HARRY B. GRAY GEORGE S. HAMMOND Pasadena, California January 196

The effect of the oceans on the terrestrial crater size-frequency distribution: Insight from numerical modeling

From the proceedings of the Workshop on Impact Craters as Indicators for Planetary Environmental Evolution and Astrobiology held in June 2006 in Östersund, Sweden.On Earth, oceanic impacts are twice as likely to occur as continental impacts, yet the effect of the oceans has not been previously considered when estimating the terrestrial crater size-frequency distribution. Despite recent progress in understanding the qualitative and quantitative effect of a water layer on the impact process through novel laboratory experiments, detailed numerical modeling, and interpretation of geological and geophysical data, no definitive relationship between impactor properties, water depth, and final crater diameter exists. In this paper, we determine the relationship between final (and transient) crater diameter and the ratio of water depth to impactor diameter using the results of numerical impact models. This relationship applies for normal incidence impacts of stoney asteroids into water-covered, crystalline oceanic crust at a velocity of 15 km s-1. We use these relationships to construct the first estimates of terrestrial crater size-frequency distributions (over the last 100 million years) that take into account the depth-area distribution of oceans on Earth. We find that the oceans reduce the number of craters smaller than 1 km in diameter by about two-thirds, the number of craters ~30 km in diameter by about one-third, and that for craters larger than ~100 km in diameter, the oceans have little effect. Above a diameter of ~12 km, more craters occur on the ocean floor than on land; below this diameter more craters form on land than in the oceans. We also estimate that there have been in the region of 150 impact events in the last 100 million years that formed an impact-related resurge feature, or disturbance on the seafloor, instead of a crater.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Do you know a CODA? Supporting Children of Deaf Adults in Their Childhood and Early Childhood Education.

The objective of this thesis was to explore what it means to be a Child of Deaf Adults (CODA) and explore the Early Childhood Education (ECE) perspective to CODAs in Finland. The development task was to create a children’s book that portrays the everyday experiences of a CODA in a relatable and authentic way. The theoretical framework of this thesis is grounded in literature exploring CODAs, Deaf culture, bilingualism, and Early Childhood Education. To gather relevant insights, we conducted two questionnaires — one for CODAs and another for ECE professionals — discovering CODAs experiences, challenges, and the support educators can provide. The book seeks to help CODA children feel seen and understood while offering educators and caregivers meaningful guidance on how to support them effectively. The key findings indicate that CODAs often navigate complex cultural and linguistic identities, balancing between the Deaf and hearing worlds. Many CODAs experience a sense of responsibility as interpreters for their parents from a young age and may struggle with belonging fully to either the Deaf or hearing community. Our research also revealed that there is little to no representation of CODAs in Finnish children’s literature, reinforcing the need for more specific literature. Based on these findings, our children's book was developed to address this gap, ensuring that CODAs can also see their experiences reflected in literature. Additionally, providing an opportunity for educators and non-CODA children to learn about diverse family dynamics. Our conclusion emphasizes the importance of increasing awareness of CODA experiences in ECE and the need for more inclusive educational resources. We recommend that future research and development projects continue to explore ways to integrate Deaf communities and CODAs representation into educational materials to foster greater inclusivity and understanding

ENABLING ONLINE CASE-BASED LEARNING FOR MANAGEMENT STUDENTS USING BLACKBOARD

The project developed a directed/supported online case study for 33 internationally-dispersed, distance learning MBA students using the Blackboard virtual learning environment (VLE). The activities included:Devising, designing and producing a case study classroom using Blackboard.Publication of a case study that could be used on the project.Development of student resources that could be used on the project.Implementation of a student application process.Co-ordination of associate tutors and Faculty.Monitoring of student diaries.Establishing evaluation system comprising depth interviews, course statistics, user statistics, questionnaire of user attitudes and observation of online behaviours.Development of an article to discuss the implications of the study

Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth

We have developed a Web-based program for quickly estimating the regional environmental consequences of a comet or asteroid impact on Earth(www.lpl.arizona.edu/ impacteffects). This paper details the observations, assumptions and equations upon which the program is based. It describes our approach to quantifying the principal impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in our predictions. The program requires six inputs: impactor diameter, impactor density, impact velocity before atmospheric entry, impact angle, the distance from the impact at which the environmental effects are to be calculated, and the target type (sedimentary rock, crystalline rock, or a water layer above rock). The program includes novel algorithms for estimating the fate of the impactor during atmospheric traverse, the thermal radiation emitted by the impact-generated vapor plume (fireball), and the intensity of seismic shaking. The program also approximates various dimensions of the impact crater and ejecta deposit, as well as estimating the severity of the air blast in both crater-forming and airburst impacts. We illustrate the utility of our program by examining the predicted environmental consequences across the United States of hypothetical impact scenarios occurring in Los Angeles. We find that the most wide-reaching environmental consequence is seismic shaking: both ejecta deposit thickness and air-blast pressure decay much more rapidly with distance than with seismic ground motion. Close to the impact site the most devastating effect is from thermal radiation; however, the curvature of the Earth implies that distant localities are shielded from direct thermal radiation because the fireball is below the horizon.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Sex Affects Myocardial Blood Flow and Fatty Acid Substrate Metabolism in Humans with Nonischemic Heart Failure

In animal models of heart failure (HF), myocardial metabolism shifts from the normal preference for high-energy fatty acid (FA) metabolism towards the more efficient fuel, glucose. However, FA (vs. glucose) metabolism generates more ATP/mole; thus FA metabolism may be especially advantageous in HF. Sex modulates myocardial blood flow (MBF) and substrate metabolism in normal humans. Whether sex affects MBF and metabolism in patients with HF is unknown. We studied 19 well-matched men and women with nonischemic HF with similar ejection fractions (all ≤ 35%). MBF and myocardial substrate metabolism were quantified using positron emission tomography. Women had higher MBF (mL/g/min), FA uptake (mL/g/min), utilization (nmol/g/min) (P<0.005, <0.005, <0.05, respectively) and trended towards higher FA oxidation than men (P=0.09). These findings were independent of age, obesity, and insulin resistance. There were no sex-related differences in fasting myocardial glucose uptake or metabolism. In an exploratory analysis of the longitudinal follow-up of these subjects (mean 7 y), we found that 4 men had a major cardiovascular event, while one woman died of non-cardiac causes. Higher MBF related to improved event-free survival (HR=0.31, P=0.02). In sum, in nonischemic HF, women have higher MBF and FA uptake and metabolism than men, and these changes are not due to differences in other variables that can affect myocardial metabolism (e.g., age, obesity, or insulin resistance). Moreover, higher MBF portends a better prognosis. These sex-related differences should be taken into account in the development and targeting of novel agents aimed at modulating in MBF and metabolism in HF

Rochechouart 2017-Drilling Campaign: First Results

No abstract available

Physiological factors affecting the rapid decrease in protein assimilation efficiency by a caterpillar on newly‐mature tree leaves

Lymantria dispar L. caterpillars have a decreased ability to assimilate protein from mature leaves of red oak ( Quercus rubra ) compared with young, expanding leaves. The present study determines whether the drop in protein assimilation efficiency (PAE) occurs during the rapid phase of leaf maturation. Several mechanisms that might account for decreased PAE are also examined: mature leaf tissues could resist being chewed efficiently, protein in mature leaf tissues could become difficult to extract, and other nutrients in mature leaves might become growth limiting. The entire seasonal decrease in PAE occurs rapidly (in less than 2 weeks), when the leaves finished expanding. The maturation process is characterized by increased levels of fibre and decreased levels of water but no significant changes in the levels of protein or carbohydrates. Despite increased fibre in mature leaves, they are not chewed into larger food particles than are immature leaves. Carbohydrate assimilation efficiencies remain high on mature leaves, and signs of limiting water levels in larvae of L. dispar on mature leaves are not observed. The most important finding in the present study is the decreased extractability of protein in food particles from mature leaves, which plays a major role in explaining the rapid decrease in PAE. It is hypothesized that structural changes in cell walls during the rapid process of leaf maturation decrease protein extractability, which, in turn, greatly decreases the nutritional quality of mature oak leaves for caterpillars. The results of the present study therefore suggest a general mechanism to help explain the widely documented decrease in the nutritional quality of the mature leaves of many tree species for herbivorous insects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106099/1/phen12049.pd