Towards understanding the interaction of water with α-Al2O3 surfaces: a sum frequency generation perspective

α-Al2O3 surfaces are omnipresent in a wide variety of applications and useful models of more complicated, environmentally abundant, alumino-silicate surfaces. Decades of work have clarified that all properties of these surfaces depend sensitively on the crystal face and the presence of even small amounts of water. This thesis aims to gain experimental insight into the interaction (adsorption structure, thermodynamic and kinetics) between water and α-Al2O3 using vibrational sum frequency generation (SFG) spectroscopy and Temperature Programmed Desorption (TPD). In the first part of this thesis, I investigate uni-molecular water interaction with α-Al2O3 under UHV conditions. By probing the OD stretching vibration of heavy water adsorbed on the α-Al2O3 (11-20) surface with SFG spectroscopy I show, in conjunction with DFT calculations, the dissociative adsorption of water on this surface leads to three types of structures: the so-called inter-CUSa/Oμ2, CUSb/Oμ2 and inter-CUSb/Oμ2 (chapter 3). In chapter 4, the desorption thermodynamics and kinetics of uni-molecule water from α-Al2O3 (0001), (1-102) and (11-20) surfaces are systematically studied experimentally using TPD. Good agreement between these results and theory are achieved on the desorption energy of uni-molecular water from α-Al2O3(11-20), (1-102) and (0001), clarifying the reactivity of the three surfaces with respect to unimolecular water dissociative adsorption is (11-20)>(1-102) >(0001) and offering substantial constraints on dissociation mechanism. In the second part of this thesis, I focus on the change in surface termination of α-Al2O3 (11-20) (chapter 5) and (0001) (chapter 6) as the surface is moved from UHV to ambient (and the water pressure increases by eight order of magnitude higher) with a SFG-DFT combined approach. The consistency between experiment and theory offers strong evidence that the (11-20) surface has in the absence of water one of four possible oxygen terminations, i.e. the so-called O-I, and that it is composed of doubly coordinated oxygen Al2O and triply coordinated Al3O in the ratio 1:2. With sub-monolayer water coverages in UHV, Al2O is protonated while Al3O is inactive. When the surface is exposed to water in ambient it is fully protonated and the stable surface structure is the O-III oxygen termination. This surface is composed of AlO, Al2O and Al3O in a ratio of 1:1:1. For the (0001) surface, it is found that termination is preparation method dependent. Preparation in UHV using annealing sputtering cycles produces one (or two possible) Al terminated surfaces, i.e. the so-called Al-I. In contrast acid etching treatment in solution yields an oxygen terminated solid because of the dissolution of the topmost Al layer (of Al-I termination). The Al-I terminated is inert with respect to water dissociative adsorption while the O-terminated (0001) is quasi instantaneously hydroxylated in air. These findings are of crucial importance in reconciling conflicting reports of basic surface properties of these materials (e.g. different measured isoelectric points or contact angles) and suggest the possibility of a new level of control of the performance of α-Al2O3 in industrial applications. As a model material, the insight into interaction between water and α-Al2O3 including the reactivities and the surface reconstruction of alumina from UHV to ambient conditions provides inspiration to understand water interaction with other environmentally abundant alumino-silicate materials. The SFG-DFT combined approaches as applied in this thesis can also be extended to other water/metal oxides systems, and would be of general interest to those interested in oxide/water interaction or the processes such interactions control.Die vorliegende Arbeit beschäftigt sich mit der Wechselwirkung zwischen Wasser und α-Al2O3 Oberflächen. Aluminiumoxid ist ein wichtiger Werkstoff für viele industrielle Anwendungen, dessen Oberflächenstruktur aber erheblichen Einfluss auf die Materialeigenschaften aufweist. Selbst geringe Mengen von Wasser verändern die Oberflächenstruktur und daraus folgend die chemischen Eigenschaften von Aluminiumoxid. Ziel dieser Arbeit ist es, Einblicke in die Wechselwirkung (Adsorptionsstruktur, Thermodynamik und Kinetik) zwischen Wasser und α-Al2O3 durch den Einsatz von optischer Schwingungsspektroskopie und Thermischer Desorptionsspektroskopie (TPD) zu gewinnen. Der erste Teil dieser Arbeit konzentriert sich auf die Untersuchung der uni-molekularen Wasserwechselwirkung mit α-Al2O3(11-20) unter UHV-Bedingungen. Die Untersuchung von OD-Steckschwingungen bei schwerem Wasser mittels Summen-Frequenz-Spektroskopie (SFG) an der Oberfläche, in Verbindung mit DFT-Berechnungen, ermöglichte die Identifikation von drei favorisierten Adsorptionsstrukturen für die Dissoziation: die sogenannte inter-CUSa/Oμ2, CUSb/Oμ2 und inter-CUSb/Oμ2. Durch Anwendung von Thermische-Desorptions-Spektroskopie (TPD) wurde ebenfalls die Desorptionskinetik von uni-molekularem Wasser auf den drei stabilsten α-Al2O3-Oberflächen (0001), (1-102) und (11-20) untersucht, was einen systematischen Einblick in die Thermodynamik und Kinetik der Wasser-Ad/Desorption ermöglichte. Die gute Übereinstimmung zwischen experimenteller und theoretischer Ergebnisse für die Desorptionsenergie deuten auf folgende abnehmende Reaktivität für Wasserdissoziation hin (11-20)>(1-102)>(0001) und zeigen die Abhängigkeit hierfür von der Koordination, Dichte und Topologie der Oberfläche auf. Der zweite Teil dieser Arbeit konzentriert sich auf die Untersuchung der morphologischen Änderung der Oberflächenstruktur von α-Al2O3 (11-20) und (0001) beim Übergang von UHV zu Umgebungsbedingungen (und dem dadurch zunehmendem relativen Wasserdruck) mittels eines kombinierten Ansatzes aus SFG und DFT. Die Konsistenz zwischen Experiment und Theorie zeigt für (11-20), dass sie in Abwesenheit von Wasser Sauerstoff terminiert ist (die sogenannte O-I Terminierung), bestehend aus doppelt koordiniertem Sauerstoff (Al2O) und dreifach koordiniertem (Al3O), im Verhältnis 1:2 ; bei geringer Wasser Adsorption(<Monolage) im UHV wird Al2O protoniert, während Al3O inaktiv ist; wenn die Oberfläche viel Wasser ausgesetzt wird (Umgebungsbedingungen), wird die Oberfläche vollständig protoniert und zu einer O-III-Termination rekonstruiert, die aus AlO, Al2O und Al3O in einem Verhältnis 1:1:1 besteht. Für die (0001)-Oberfläche wurde gezeigt, dass die Terminierung präparations Abhängig ist: bei der Präparation im UHV mit Heiz- und Sputter-Zyklen erzeugt man eine Al-terminierte Oberfläche, die sogenannte Al-I Terminierung. Im Gegensatz hierzu führt die Säureätzbehandlung zu einer O-I Terminierung aufgrund der Auflösung der obersten Al-Schicht der Al-I Terminierung. Die Al-I ist inert gegenüber dissoziativer Adsorption, während die O-Terminierung (0001) sofort in Luft hydroxyliert wird. Diese Ergebnisse sind von entscheidender Bedeutung, um die unterschiedlichen Oberflächeneigenschaften zu verstehen, die in verschiedensten vorhergehenden Arbeiten durch IEPs, Wasserkontaktwinkel usw. beobachtet wurden; ebenfalls eröffnen die Erkenntnisse Möglichkeiten, um die Eigenschaften von α-Al2O3 in Industrieanwendungen zu verstehen und möglicherweise zu kontrollieren. Zusammenfassend liefert das untersuchte Modelsystem Einblicke in die Interaktion zwischen Wasser und α-Al2O3, einschließlich der Reaktivitäten und der Oberflächenrekonstruktion beim Übergang von UHV zu Umgebungsbedingungen und fördert das Verständnis der Wasserwechselwirkung mit anderen in der Umwelt vorkommenden Aluminium-Silikatmaterialien. Der kombinierte SFG und DFT Ansatz, wie er in dieser Arbeit angewendet wurde, kann auch auf andere Wasser/Metalloxidsysteme ausgedehnt werden und wäre somit von allgemeinem Interesse für Arbeiten, die an einer Oxid/Wasser-Wechselwirkung, sowie der Kontrolle der dabei ablaufenden Prozesse interessiert sind

Lactic acid bacteria with a strong antioxidant function isolated from “Jiangshui,” pickles, and feces

Excessive free radicals and iron death lead to oxidative damage, which is one of the main causes of aging and diseases. In this field of antioxidation, developing new, safe, and efficient antioxidants is the main research focus. Lactic acid bacteria (LAB) are natural antioxidants with good antioxidant activity and can regulate gastrointestinal microecological balance and immunity. In this study, 15 LAB strains from fermented foods (“Jiangshui” and pickles) or feces were evaluated in terms of their antioxidant attributes. Strains with strong antioxidant capacity were preliminarily screened by the following tests: 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radical, superoxide anion radical scavenging capacity; ferrous ion chelating assay; hydrogen peroxide tolerance capacity. Then, the adhesion of the screened strains to the intestinal tract was examined using hydrophobic and auto-aggregation tests. The safety of the strains was analyzed based on their minimum inhibitory concentration and hemolysis, and 16S rRNA was used for molecular biological identification. Antimicrobial activity tests showed them probiotic function. The cell-free supernatant of selected strains were used to explore the protective effect against oxidative damage cells. The scavenging rate of DPPH, hydroxyl radicals, and ferrous ion-chelating of 15 strains ranged from 28.81–82.75%, 6.54–68.52%, and 9.46–17.92%, respectively, the scavenging superoxide anion scavenging activity all exceeded 10%. According to all the antioxidant-related tests, strains possessing high antioxidant activities J2-4, J2-5, J2-9, YP-1, and W-4 were screened, these five strains demonstrated tolerance to 2 mM hydrogen peroxide. J2-4, J2-5, and J2-9 were Lactobacillus fermentans and γ-hemolytic (non-hemolytic). YP-1 and W-4 were Lactobacillus paracasei and α-hemolytic (grass-green hemolytic). Although L. paracasei has been proven as a safe probiotic without hemolytic characteristics, the hemolytic characteristics of YP-1 and W-4 should be further studied. Due to the weak hydrophobicity and antimicrobial activity of J2-4, finally, we selected J2-5, J2-9 for cell experiment, J2-5 and J2-9 showed an excellent ability that resistant to oxidative damage by increasing SOD, CAT, T-AOC activity of 293T cells. Therefore, J2-5, and J2-9 strains from fermented foods “Jiangshui” could be used as potential antioxidants for functional food, health care, and skincare

NO SPACE LEFT BEHIND - Graduate Urban Design Studio - LANDARCH 606

The following report documents the work of the 2015 Spring Graduate Urban Design Studio course in the Department of Landscape Architecture and Regional Planning. This fourteen week studio focused on using tactical urbanism to engage Springfield’s Metro Center neighborhood with visions to revitalize the downtown core of this legacy city. In addition to completing the components of a traditional urban design studio (site analyses, schematic plans, spatial designs, and programming), the student teams also developed conceptual projects to immediately engage the public. These efforts culminated in a free afternoon walking tour throughout the Metro Center that presented several tactical interventions. These interactive, public installations illustrated potential future initiatives and brought attention to overlooked areas and assets. Throughout the semester the teams were challenged to continuously consider both the short-term impacts of their interventions and the long-term visions for the future of Springfield’s urban core. This strategy allowed students to develop a process-based approach to urban design. It provided opportunities to engage stakeholders and test new ideas with the public, rather than simply creating a master plan without any real world interactions with the city and its populace. STUDIO GOALS • To enliven public space in Springfield’s Metro Center through small-scale urban design interventions which illustrate and inform long-term plans • To activate residual spaces in the downtown with Tactical Urbanism By matching long-term visions for the Metro Center with short-term, site-specific tactical interventions the teams were able to deliver a variety of ideas in multiple formats. Furthermore, the experience of interacting with community members during the installation of projects added a great deal of meaning to the research and design process. The work explores a community service learning strategy within the framework of an urban design studio with the goal of revitalizing the city of Springfield, Massachusetts, through sustainable design, planning, and engagement with the community. The six design-team interventions are documented and published as team-authored videos: 1. Union Station Green Corridor Maozhu Mao, Yuqing Wu https://www.youtube.com/watch?v=EnE8Yt8x0Es&feature=youtu.be 2. (No) Vacancy Chris Counihan, Michalagh Stoddard, Ruoying Tang https://youtu.be/CapaQ9gDxeM 3. Extra Space, Active Street Yu Yu https://youtu.be/2pgYq5HLNHA 4. Spring into Art Emilie Jordao, Matt Hisle, Jing Wang https://youtu.be/Vf2yk6Se6rU 5. Urban Agua Kellie Fenton, James Prendergast, Nelle Ward https://www.youtube.com/watch?v=vk2PUJMdhTU&feature=youtu.be 6. Make the Connection Yue Li, Yanhua Lu, Yi Yang https://youtu.be/EvQD0QYV97

Mode-division multiplexed transmission with inline few-mode fiber amplifier

We demonstrate mode-division multiplexed WDM transmission over 50-km of few-mode fiber using the fiber\u27s LP01 and two degenerate LP11 modes. A few-mode EDFA is used to boost the power of the output signal before a few-mode coherent receiver. A 6x6 time-domain MIMO equalizer is used to recover the transmitted data. We also experimentally characterize the 50-km few-mode fiber and the few-mode EDFA

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead