172 research outputs found
kowarik-labs/AI-reflectivity: v0.1
No full textAI-reflectivity is a code based on artificial neural networks trained with simulated reflectivity data that quickly predicts film parameters from experimental X-ray reflectivity curves. This project has a common root with (ML-reflectivity)[https://github.com/schreiber-lab/ML-reflectivity] and evolved in parallel. Both are linked to the follwoing publication:
Fast Fitting of Reflectivity Data of Growing Thin Films Using Neural Networks A. Greco, V. Starostin, C. Karapanagiotis, A. Hinderhofer, A. Gerlach, L. Pithan, S. Liehr, F. Schreiber, S. Kowarik (2019). J. Appl. Cryst.
For an online live demonstration using a pre-trained network have a look at github
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Effects of pendent phenol functional groups on secondary coordination spheres of heme like Fe-salen complexes
No full textSince the beginning of industrial revolution, burning of fossil fuels has mainly led to increase in atmospheric concentration of CO2 , a Green House Gas (GHG), from 250 ppm to 400 ppm between 1800 and 2012. One way to reduce the burning of fossil fuels and CO2 emission rate is to explore alternative carbon free fuels to meet the energy demand.This project aims at the synthesis and study of metal complexes inspired by biological models that will help better design catalysts to perform water oxidation more effectively.This poster won the Dean, Faculty of Science award (2020). Advisor: Dr. Linus Chiang, Departmen of Chemistry
Temperature dependent investigation of PTCDI-C8 thin film structure
No full textLAUREA MAGISTRALEAl giorno d’oggi, i settori dei dispositivi elettronici ed optoelettronici
stanno sviluppando applicazioni basate su semiconduttori
organici e sullo studio della morfologia dei film sottili di tali materiali
al fine di determinare e modulare le prestazioni e l’efficienza dei
dispositivi.
In particolare, questa tesi si occupa dello studio di film sottili di
PTCDI-C8, un semiconduttore organico di tipo n costituito da molecole
coniugate che ha dimostrato di avere potenziale applicativo
nell’optoelettronica organica, come le celle solari organiche, e nell’elettronica,
come i transistor organici ad effetto di campo. In questo
caso, un parametro importante che influenza le prestazioni e l’efficienza
dei dispositivi è la mobilità dei portatori liberi di carica. Per
comprendere meglio come questo aspetto possa essere sviluppato,
sono necessari studi sulla morfologia del film sottile.
Nel quadro di questa tesi verrà presentato uno studio a monte dell’evoluzione
della morfologia di film sottile di PTCDI-C8 al variare
della temperatura. In particolare, l’attenzione sarà focalizzata sull’evoluzione
della struttura cristallina a diverse temperature, analizzando
i parametri della cella unitaria e le loro modifiche.
Nella prima parte verrà illustrata un’introduzione relativa ai semiconduttori
organici e al PTCDI-C8. In seguito, verrà fornita una
panoramica delle tecniche e dei metodi sperimentali utilizzati per
studiare la struttura a cristalli del film sottile: tecniche a raggi X
e metodo di crescita del film secondo deposito di molecole organiche.
Quindi, saranno discussi i risultati sperimentali. Si è visto
che i parametri della cella unitaria del film sottile di PTCDI-C8 al
variare della temperatura seguono una tendenza, e alla temperatura
di T=200°C appare una diversa struttura cristallina osservata
attraverso misure di diffrazione con piccoli angoli di incidenza.Nowadays, the fields of electronic and opto-electronic devices
are basing future applications on organic semiconductors and on
the study of thin film morphology made up by those materials, in
order to determine and tailor the performances and the efficiency of
the devices.
In particular, this thesis deals with thin films of PTCDI-C8, a ntype
organic semiconductor made up by conjugated molecule which
has proven to have potential in organic opto-electronics, such as organic
solar cells, and organic electronics, such as organic field effect
transistors. In this case, an important parameter that influences the
performances and the efficiency of the devices is the charge carrier
mobility. In order to better understand how this aspect can be tailored,
studies on the thin film morphology are necessary.
In the framework of this thesis an upstream study of the PTCDI-C8
thin film morphology evolution with temperature changes will be
presented. In particular the focus will be on the evolution of the
crystal structure at different temperatures, analyzing the unit cell
parameters and their modifications.
In the first part an introduction regarding organic semiconductors
and PTCDI-C8 will be illustrated. Then an overview of the experimental
techniques and methods used to study the thin film crystal
structure will be provided: X-ray techniques and organic molecular
beam deposition growth method. Afterwards, the experimental results
will be discussed. It has been seen that PTCDI-C8 unit cell
parameters follow a trend while changing the temperature, and at
the temperature of T=200°C a different crystal structure appears
from grazing incident X-ray diffraction measurements
21st-century scholarship and Wikipedia
No full textWikipedia, the world’s fifth most-used Web site, is a good illustration of the growing credibility of online resources. In his article in Ariadne earlier this year, “Wikipedia: Reflections on Use and Academic Acceptance”, Brian Whalley described the debates around accuracy and review, in the context of geology. He concluded that ‘If Wikipedia is the first port of call, as it already seems to be, for information requirement traffic, then there is a commitment to build on Open Educational Resources (OERs) of various kinds and improve their quality.’ In a similar approach to the Geological Society event that Whalley describes, Sarah Fahmy of JISC worked with Wikimedia and the British Library on a World War One (WWI) Editathon. There is a rich discourse about the way that academics relate to Wikipedia
On the role of external stimuli to tailor growth of organic thin films
No full textIn dieser Arbeit werden neue Strategien zur Wachstumskontrolle funktionaler organischer Dünnschichtmaterialien aufgezeigt, mit denen sich die Eigenschaften molekularer Schichtsysteme gezielt beeinflussen lassen. Ein Fokus liegt dabei auf der Untersuchung des Einflusses von optischen Feldern auf das Wachstumsverhalten. Ein weiterer Schwerpunkt wird auf das Grundlagenverständnis von thermisch aktivierten, kinetischen Prozessen, die die Morphologie während und nach dem Schichtwachstum beeinflussen, gelegt. Zuerst wird am Beispiel des molekularen Halbleiters Sexithiophen (6T) gezeigt, wie sich Kontrolle über das Kristallphasengleichgewicht während des Wachstums auf Kaliumchlorid (KCl) erzielen lässt. Im zweiten Teil der Arbeit wird eine neue Herangehensweise zur direkten Ausrichtung von Molekülkristallen im optischen Feld während ihrer Entstehung studiert. Am Beispiel von Tetracene wird gezeigt wie sich so optische anisotrope Absorptionseigenschaften von Molekülen dazu nutzen lassen den Brechungsindex eines polykristallinen Films lokal durch ein photolitographisches Verfahren zu beeinflussen. Im dritten Teil wird der Einfluss von dynamisch variierenden Wachstumsbedingungen während des Schichtwachstums von PTCDI-C8 studiert. Es wird gezeigt, dass sich die Oberflächenrauigkeit stark reduzieren lässt, indem zu Beginn des Wachstums jeder individuellen molekularen Monolage die Nukleationsdichte stark erhöht und in den darauf folgenden Wachstumsphasen die Diffusivität gezielt gesteigert wird. Im vierten Teil wird das Diffusionsverhalten von n-Alkan Schichten unter thermischen Einflüssen betrachtet. Es wird gezeigt, dass die inhärente molekulare Anisotropie von C44H90 Molekülen (TTC) sowie die sehr geringe, stark anisotrope, Oberflächenenergie dieses Materials ein ungewöhnliches Diffusionsverhalten auslöst.The research performed in the framework of this thesis focuses on new strategies to effectively control the growth of crystalline thin films of functional organic molecules and attributes the quest for additional growth control parameters in organic molecular beam deposition (OMBD). First the influence of light on the growth process of the sexithiophene (6T) is studied. We find that 6T thin films deposited as conventional in dark environments on KCl exhibit a bimodal growth with phase coexistence of two crystal polymorphs. In contrast, films grown under illumination with 532 nm light show increased phase purity. Further, we establish light-directed molecular self-assembly (LDSA) to generate permanently aligned thin films of tetracene (C18H12) and demonstrate direct patterning with light. Polarized light illumination leads to azimuthally photoaligned films on isotropic, amorphous substrates. Thus, LDSA can be regarded as a new degree of freedom in the quest for control-parameters in organic thin film growth. Next the impact of dynamic temperature oscillations on the time scales of molecular monolayer growth during organic molecular beam deposition is discussed. We strongly increase the island density during nucleation and selectively increase interlayer diffusion at later stages of monolayer growth. We analyse the interplay between molecular interlayer transport and island sizes to understand kinetic processes during growth. In a fourth experiment we show how thermal annealing can be used to improve smoothness and to increase the lateral size of crystalline islands of n-alkane (TTC, C44H90) films. We employ real-time optical phase contrast microscopy to track the diffusion across monomolecular step edges which causes the unusual smoothing during annealing. We rationalise the smoothing behaviour with the highly anisotropic attachment energies and low surface energies of TTC
How Many Answers Are Enough? Optimal Number of Answers for Q&A Sites
No full textWith the proliferation of the social web, questions about information quality and optimization attract the attention of IS scholars. Question-answering (QA) sites, such as Yahoo!Answers, have the potential to produce good answers, but at the same time not all answers are good and not all QA sites are alike. When organizations design and plan for the integration of question answering services on their sites, identification of good answers and process optimization become critical. Arguing that ‘given enough answers all questions are answered successfully,’ this paper identifies the optimal number of posts that generate high quality answers. Based on content analysis of Yahoo! Answers’ informational questions (n=174) and their answers (n=1,023), the study found that seven answers per question are ‘enough’ to provide a good answer
Power Relations and Social Classes in Pengakuan Pariyem by Linus Suryadi AG: Reflection of Masculine Ideology
No full textThe study aims to explore power relations and social classes as the reflections of the masculine ideology of the author in the novel Pengakuan Pariyem by Linus Suryadi AG. The theories implemented in the study are van Dijk’s power relations and social classes theory and Connell’s masculinity theory. The study is qualitative descriptive and applies the Critical Discourse Analysis (CDA) method, used to dismantle the ideology that is produced and reproduced through the language within the novel. The research data are lingual units that indicate power relations and social classes which simultaneously reflect the notion of masculinity. The results of the study are as follows. First, Pariyem as the central character in the novel lives within a hierarchical and dualistic Javanese society. Her submission as the babu (housemaid) of a priyayi (noble) family does not only lead Pariyem to be dominated symbolically, but also legitimizes the priyayi (aristocrats) power over wong cilik (commoners). It is reinforced by the representations of the priyayis’ world views in terms of culture, aristocracy, bureaucracy, and education orientation. It shows that priyayis are culturally dominant. Secondly, since Pariyem is a character created by a male author, her behaviors and actions reflect the ideology of masculinity. Rather than voicing women, the power relations that Pariyem experiences through the events constructed in the novel show that she embodies the masculine ideology, or masculinity.
Linus Pauling.
No full textDigital ImageAmerican chemist, biochemist, peace activist and author. For his scientific work, Pauling was awarded the Nobel Prize in Chemistry in 1954; and for his peace activism, he was awarded the Nobel Peace Prize in 1962
March for Science: Sign with a quote from scientists Linus Pauling, E. Pine St. at Belmont Ave., Seattle, Washington, April 22, 2017
No full textText on signs read: "No science = No hops, no malt, no water, no beer [the letters in the word beer are made up of periodic element symbols]"; "Facts are the air of scientists. Without them you can never fly. - Linus Pauling. Science, not silence".
Linus Carl Pauling was an American chemist, biochemist, peace activist, author, and educator.
PH Coll 1478. KinseyK116The Seattle March for Science occurred on April 22, 2017. This date was chosen because April 22 is also Earth Day. According to organizers, as many as 20,000 people attended the march, which began at 10 a.m. in Cal Anderson Park in the Capitol Hill neighborhood. The march culminated at the International Fountain at the Seattle Center. The March for Science in Seattle was one of more than 500 similar marches taking place across the United States. Demonstrators marched in support of “robustly funded and publicly communicated science and evidence as a pillar of human freedom and prosperity” and also called “for science that upholds the common good, and for political leaders and policymakers to enact evidence-based policies in the public interest”, according to a statement put out by march organizers. Washington Governor Jay Inslee and Seattle Mayor Ed Murray came out to show their support.Scienc
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