513 research outputs found
Using Green Chemistry to Build Community: How Transformational Learning Impacts the Building of a Community of Practice
Green Chemistry education is a widening field, seeking to include educators at all levels collaboratively in the process of transforming outdated chemistry practices. Qualitative research methods were used to interview three key collaborator groups at Beyond Benign, a green chemistry education organization, who are considered part of the Green Chemistry Community of Practice (GCCoP). This was done to develop a strategic plan to 1) explore how the Beyond Benign team and K-12 teachers see themselves as part of one GCCoP; 2) to ascertain how to bring the K-12 program into alignment with the organizationâs evolving mission; and 3) to discover approaches for improving K-12 and Higher Ed collaboration and engagement, creating new possibilities for K-12, and bringing the two communities back into one evolving GCCoP. What was discovered through interviews with the Beyond Benign team, K-12 teachers, and higher ed faculty was that there were several challenges, but many possibilities for collaboration. Transformational learning that generates engagement, agency, and a desire for change was a theme that educators at all levels, from elementary through grad school, described as important to learning and building community around green chemistry to generate changes in the wider world, and draw more people into GCCoP
A quantum crystallographic approach to study properties of molecules in crystals
In this dissertation, the behaviour of atoms, bonds, functional groups and molecules in vacuo
but especially also in the crystal is studied using quantum crystallographic methods. The goal
is to deepen the understanding of the properties of these building blocks as well as of the
interactions among them, because good comprehension of the microscopic units and their
interplay also enables us to explain the macroscopic properties of crystals.
The first part (chapters 1-3) and second part (chapter 4) of this dissertation contain theoretical
introductions about quantum crystallography. On the one hand, this expression contains
the termquantum referring to quantumchemistry. Therefore, the very first chapter gives a
brief overview about this field. The second chapter addresses different options to partition
quantum chemical entities, such as the electron density or the bonding energy, into their
components. On the other hand, quantumcrystallography consists obviously of the crystallographic
part and chapter 3 covers these aspects focusing predominantly on X-ray diffraction.
A more detailed introduction to quantum crystallography itself is presented in the second part
(chapter 4).
The third part (chapters 5-9) starts with an overview of the goals of this work followed by the
results organized in four chapters.
The goal is to deepen the understanding of properties of crystals by theoretically analysing
their building block. It is for example studied how electrons and orbitals rearrange due to the
electric field in a crystal or how high pressure leads to the formation of new bonds. Ultimately,
these findings shall help to rationally design materials with desired properties such as high
refractive index or semiconductivity.Mithilfe quantenkristallografischer Methoden werden Atome, Bindungen, funktionellen Gruppen
und MolekĂŒle in vacuo aber vor allem auch in Kristallen untersucht. Das Ziel ist es die
Eigenschaften dieser Bestandteile zu verstehen und wie sie miteinander interagieren. Das
VerstÀndnis der Verhaltensweise der einzelnen Bausteine sowie deren Zusammenspiel auf
mikroskopischer Ebene kann auch die makroskopischen Eigenschaften von Kristallen erklÀren.
Der erste Teil dieser Doktorarbeit (Kapitel 1-3) beinhaltet eine theoretische Einleitung in die
verschiedenen Bereiche der Quantenkristallografie. Wie der Name Quantenkristallografie
besagt, besteht diese zum einen aus dem quantenchemischen Teil, weswegen das erste Kapitel
eine kurze EinfĂŒhrung in die Quantenchemie gibt. Das zweite Kapitel widmet sich den verschiedenen Möglichkeiten
quantenchemische Grössen wie zum Beispiel die Elektronendichte
oder Bindungsenergien in Einzelteile zu zerlegen. Zum anderen trÀgt der kristallografische
Teil zur Quantenkristallografie bei. Kapitel drei besteht daher aus einem kurzen Ăberblick
ĂŒber die Kristallografie mit Fokus auf der Röntgenbeugung.
Anschliessend folgt im zweiten Teil (Kapitel 4) eine ausfĂŒhrlichere Einleitung in die Quantenkristallografie
selbst.
Der dritte Teil (Kapitel 5-9) beginnt mit einer kurzen Ăbersicht ĂŒber die Ziele dieser Arbeit
worauf die Resultate, gegliedert in vier verschiedene Kapitel, folgen.
Das Ziel dieser Arbeit ist es die Eigenschaften von Kristallen besser zu verstehen, indem
man ihre Einzelteile theoretisch analysiert und mit verschiedenen Methoden rationalisiert.
Beispielsweise wird untersucht wie sich Elektronen und Orbitale aufgrund des elektrischen
Feldes in Kristallen neu anordnen oder wie unter hohem Druck Bindungen neu geformt
werden. Schlussendlich können all diese Erkenntnisse helfen, Materialien mit spezifischen
gewĂŒnschten Eigenschaften herzustellen.Les atomes, les liaisons entre eux, les groupes fonctionnels et les molĂ©cules sont examinĂ©s
en utilisant des méthodes de la cristallographie quantique. Le but est de comprendre les
propriétés de ces composants et comment ils interagissent in vacuo mais surtout aussi dans
les cristaux. En comprenant leurs caractéristiques et interactions au niveau microscopique,
on peut aussi rationaliser les propriétés macroscopiques des cristaux.
La premiĂšre partie (chapitres 1-3) de cette thĂšse de doctorat contient une introduction brĂšve Ă
la cristallographie quantique. Comme le nomlâindique, ce domaine de recherche est composĂ©
de la chimie quantique et la cristallographie. Pour cette raison le premier chapitre donne
une introduction à la chimie quantique. Le deuxiÚme chapitre présente quelques méthodes
de décomposition des quantités de la chimie quantique comme la densité électronique ou
lâĂ©nergie de liaison. Le troisiĂšme chapitre couvre la partie cristallographique.
Ensuite dans la deuxiÚme partie (chapitre 4) une introduction plus détaillée sur la cristallographie
quantique elle-mĂȘme est donnĂ©e.
La troisiÚme partie (chapitres 5-9) commence par un aperçu des objectives de cette dissertation
suivis des résultats structurés en quatre chapitres.
Le but est de comprendre les propriétés des cristaux en analysant leurs building blocks avec
différentes méthodes théoriques. Il était par example examiné comment les électrons et
les orbitales se réorganisent dans un cristal à cause du champ électrique ou comment des
nouvelles liaisons sont formées sous pression. Finalement on peut utiliser ces conclusions
pour modeler des matériaux avec des propriétés désirées
Endangered by Sprawl: How Runaway Development Threatens America's Wildlife
Estimates the growth of land consumption in metropolitan areas over the next 25 years, investigates locally implemented strategies to protect natural lands from overdevelopment, and offers "smart growth" as an option for reducing suburban sprawl
Strength and Nature of HostâGuest Interactions in MetalâOrganic Frameworks from a QuantumâChemical Perspective
Metal-organic frameworks (MOFs) offer a convenient means for capturing, transporting, and releasing small molecules. Their rational design requires an in-depth understanding of the underlying non-covalent host-guest interactions, and the ability to easily and rapidly pre-screen candidate architectures in silico. In this work, we devised a recipe for computing the strength and analysing the nature of the host-guest interactions in MOFs. By assessing a range of density functional theory methods across periodic and finite supramolecular cluster scale we find that appropriately constructed clusters readily reproduce the key interactions occurring in periodic models at a fraction of the computational cost. Host-guest interaction energies can be reliably computed with dispersion-corrected density functional theory methods; however, decoding their precise nature demands insights from energy decomposition schemes and quantum-chemical tools for bonding analysis such as the quantum theory of atoms in molecules, the non-covalent interactions index or the density overlap regions indicator
Engineering HostâGuest Interactions in Organic Framework Materials for Drug Delivery
Metal-organic frameworks (MOF) and covalent organic frameworks (COFs) are promising nanocarriers for targeted drug delivery. Noncovalent interactions between frameworks and drugs play a fundamental role in the therapeutic uptake and release of the latter. However, the scope of framework functionalizations and deliverable drugs remains underexplored. Using a multilevel approach combining molecular docking and density functional theory, we show for a range of drugs and frameworks that experimentally reported release metrics are in good agreement with the in silico computed hostâguest interaction energies. Functional groups within the framework significantly impact the strength of these hostâguest interactions, while a given framework can serve as an efficient delivery agent for drugs beyond the prototypical few. Our findings identify the interaction energy as a reliable and relatively easy to compute descriptor of organic framework materials for drug delivery, able to facilitate their high-throughput screening and targeted design towards extended-release times
Disconnected: Poverty, Water Supply and Development in Jakarta, Indonesia
human development, water, sanitation
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The Regional Response to Federal Funding for Bicycle and Pedestrian Projects
Examines the efficacy of federal funding for non-motorized modes of transportation based on funding patterns across metropolitan regions, case studies of policies and projects, and an analysis of the funding's impact on bicycling and walking behavior
Hostâguest interactions in framework materials:Insight from modeling
The performance of metalâorganic and covalent organic framework materials in sought-after applicationsâcapture, storage, and delivery of gases and molecules, and separation of their mixturesâheavily depends on the hostâguest interactions established inside the pores of these materials. Computational modeling provides information about the structures of these hostâguest complexes and the strength and nature of the interactions present at a level of detail and precision that is often unobtainable from experiment. In this Review, we summarize the key simulation techniques spanning from molecular dynamics and Monte Carlo methods to correlate ab initio approaches and energy, density, and wavefunction partitioning schemes. We provide illustrative literature examples of their uses in analyzing and designing organic framework hosts. We also describe modern approaches to the high-throughput screening of thousands of existing and hypothetical metalâorganic frameworks (MOFs) and covalent organic frameworks (COFs) and emerging machine learning techniques for predicting their properties and performances. Finally, we discuss the key methodological challenges on the path toward computation-driven design and reliable prediction of high-performing MOF and COF adsorbents and catalysts and suggest possible solutions and future directions in this exciting field of computational materials science
Locating Guest Molecules inside MetalâOrganic Framework Pores with a Multilevel Computational Approach
Molecular docking has traditionally mostly been employed in the field of proteinâligand binding. Here, we extend this method, in combination with DFT-level geometry optimizations, to locate guest molecules inside the pores of metalâorganic frameworks. The position and nature of the guest molecules tune the physicochemical properties of the hostâguest systems. Therefore, it is essential to be able to reliably locate them to rationally enhance the performance of the known metalâorganic frameworks and facilitate new material discovery. The results obtained with this approach are compared to experimental data. We show that the presented method can, in general, accurately locate adsorption sites and structures of the hostâguest complexes. We therefore propose our approach as a computational alternative when no experimental structures of guest-loaded MOFs are available. Additional information on the adsorption strength in the studied hostâguest systems emerges from the computed interaction energies. Our findings provide the basis for other computational studies on MOFâguest systems and contribute to a better understanding of the structureâinteractionâproperty interplay associated with them
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